diff --git a/src/hir/serialise.cpp b/src/hir/serialise.cpp
index 8336a590..6d0473c1 100644
--- a/src/hir/serialise.cpp
+++ b/src/hir/serialise.cpp
@@ -842,8 +842,8 @@
                 ),
             (If,
                 serialise(e.cond);
-                m_out.write_count(e.bb0);
-                m_out.write_count(e.bb1);
+                m_out.write_count(e.bb_true);
+                m_out.write_count(e.bb_false);
                 ),
             (Switch,
                 serialise(e.val);
diff --git a/src/hir_conv/constant_evaluation.cpp b/src/hir_conv/constant_evaluation.cpp
index 292760d1..fd2a1ce3 100644
--- a/src/hir_conv/constant_evaluation.cpp
+++ b/src/hir_conv/constant_evaluation.cpp
@@ -2016,7 +2016,7 @@ namespace HIR {
         TU_ARMA(If, e) {
             bool res = U128(0) != local_state.get_lval(e.cond).read_uint(state, 1);
             DEBUG(state << " IF " << res);
-            return res ? e.bb1 : e.bb0;
+            return res ? e.bb_true : e.bb_false;
             }
         TU_ARMA(Switch, e) {
             HIR::TypeRef    tmp;
diff --git a/src/mir/check.cpp b/src/mir/check.cpp
index 4590d807..dc22061f 100644
--- a/src/mir/check.cpp
+++ b/src/mir/check.cpp
@@ -575,8 +575,8 @@ void MIR_Validate_ValState(::MIR::TypeResolve& state, const ::MIR::Function& fcn
         TU_ARMA(If, e) {
             // Push blocks
             val_state.ensure_valid( state, e.cond );
-            add_to_visit_copy( e.bb0, path, val_state );
-            add_to_visit_move( e.bb1, mv$(path), mv$(val_state) );
+            add_to_visit_copy( e.bb_true , path, val_state );
+            add_to_visit_move( e.bb_false, mv$(path), mv$(val_state) );
             }
         TU_ARMA(Switch, e) {
             val_state.ensure_valid( state, e.val );
@@ -684,8 +684,8 @@ void MIR_Validate(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path
                 PUSH_BB(e.dst, "Panic");
                 ),
             (If,
-                PUSH_BB(e.bb0, "If true");
-                PUSH_BB(e.bb1, "If false");
+                PUSH_BB(e.bb_true , "If true");
+                PUSH_BB(e.bb_false, "If false");
                 ),
             (Switch,
                 for(unsigned int i = 0; i < e.targets.size(); i++ ) {
diff --git a/src/mir/check_full.cpp b/src/mir/check_full.cpp
index 06f0548c..29cf3915 100644
--- a/src/mir/check_full.cpp
+++ b/src/mir/check_full.cpp
@@ -966,8 +966,8 @@ void MIR_Validate_FullValState(::MIR::TypeResolve& mir_res, const ::MIR::Functio
             ),
         (If,
             state.ensure_lvalue_valid(mir_res, te.cond);
-            todo_queue.push_back( ::std::make_pair(te.bb0, state.clone()) );
-            todo_queue.push_back( ::std::make_pair(te.bb1, mv$(state)) );
+            todo_queue.push_back( ::std::make_pair(te.bb_true, state.clone()) );
+            todo_queue.push_back( ::std::make_pair(te.bb_false, mv$(state)) );
             ),
         (Switch,
             state.ensure_lvalue_valid(mir_res, te.val);
diff --git a/src/mir/dump.cpp b/src/mir/dump.cpp
index 4f30a66f..b6b8c1fe 100644
--- a/src/mir/dump.cpp
+++ b/src/mir/dump.cpp
@@ -155,7 +155,7 @@ namespace {
                     m_os << "panic bb" << e.dst << ";\n";
                     ),
                 (If,
-                    m_os << "if " << FMT_M(e.cond) << " { goto bb" << e.bb0 << "; } else { goto bb" << e.bb1 << "; }\n";
+                    m_os << "if " << FMT_M(e.cond) << " { goto bb" << e.bb_true << "; } else { goto bb" << e.bb_false << "; }\n";
                     ),
                 (Switch,
                     m_os << "switch " << FMT_M(e.val) << " {";
diff --git a/src/mir/helpers.cpp b/src/mir/helpers.cpp
index 8d7d6293..0b66c5fa 100644
--- a/src/mir/helpers.cpp
+++ b/src/mir/helpers.cpp
@@ -998,8 +998,8 @@ void MIR_Helper_GetLifetimes_DetermineValueLifetime(
                 m_states_to_do.push_back( ::std::make_pair(te.dst, mv$(state)) );
                 }
             TU_ARMA(If, te) {
-                m_states_to_do.push_back( ::std::make_pair(te.bb0, state.clone()) );
-                m_states_to_do.push_back( ::std::make_pair(te.bb1, mv$(state)) );
+                m_states_to_do.push_back( ::std::make_pair(te.bb_true, state.clone()) );
+                m_states_to_do.push_back( ::std::make_pair(te.bb_false, mv$(state)) );
                 }
             TU_ARMA(Switch, te) {
                 for(size_t i = 0; i < te.targets.size(); i ++)
diff --git a/src/mir/helpers.hpp b/src/mir/helpers.hpp
index cfd183d2..203e4d64 100644
--- a/src/mir/helpers.hpp
+++ b/src/mir/helpers.hpp
@@ -430,8 +430,8 @@ namespace visit {
                 }
             TU_ARMA(If, e) {
                 rv |= visit_lvalue(e.cond, ValUsage::Read);
-                rv |= visit_block_id(e.bb0);
-                rv |= visit_block_id(e.bb1);
+                rv |= visit_block_id(e.bb_true);
+                rv |= visit_block_id(e.bb_false);
                 }
             TU_ARMA(Switch, e) {
                 rv |= visit_lvalue(e.val, ValUsage::Read);
diff --git a/src/mir/mir.cpp b/src/mir/mir.cpp
index 22544e7e..599e66c9 100644
--- a/src/mir/mir.cpp
+++ b/src/mir/mir.cpp
@@ -425,7 +425,7 @@ namespace MIR {
             os << "Panic(" << e.dst << ";)";
             ),
         (If,
-            os << "If( " << e.cond << " : " << e.bb0 << ", " << e.bb1 << ")";
+            os << "If( " << e.cond << " : " << e.bb_true << ", " << e.bb_false << ")";
             ),
         (Switch,
             os << "Switch( " << e.val << " : ";
@@ -498,9 +498,9 @@ namespace MIR {
         (If,
             if( ae.cond != be.cond )
                 return false;
-            if( ae.bb0 != be.bb0 )
+            if( ae.bb_true != be.bb_true )
                 return false;
-            if( ae.bb1 != be.bb1 )
+            if( ae.bb_false != be.bb_false )
                 return false;
             ),
         (Switch,
diff --git a/src/mir/mir.hpp b/src/mir/mir.hpp
index 4c9ed00e..f4024bd4 100644
--- a/src/mir/mir.hpp
+++ b/src/mir/mir.hpp
@@ -615,8 +615,8 @@ TAGGED_UNION(Terminator, Incomplete,
     (Panic, struct { BasicBlockId dst; }),  // ?
     (If, struct {
         LValue cond;
-        BasicBlockId    bb0;    // true
-        BasicBlockId    bb1;    // false
+        BasicBlockId    bb_true;
+        BasicBlockId    bb_false;
         }),
     (Switch, struct {
         LValue val;
diff --git a/src/mir/optimise.cpp b/src/mir/optimise.cpp
index 476c6418..1861f178 100644
--- a/src/mir/optimise.cpp
+++ b/src/mir/optimise.cpp
@@ -802,8 +802,8 @@ namespace
             cb(e.dst);
             }
         TU_ARMA(If, e) {
-            cb(e.bb0);
-            cb(e.bb1);
+            cb(e.bb_true );
+            cb(e.bb_false);
             }
         TU_ARMA(Switch, e) {
             for(auto& target : e.targets)
@@ -1462,8 +1462,8 @@ bool MIR_Optimise_Inlining(::MIR::TypeResolve& state, ::MIR::Function& fcn, bool
             (If,
                 return ::MIR::Terminator::make_If({
                     this->clone_lval(se.cond),
-                    se.bb0 + this->bb_base,
-                    se.bb1 + this->bb_base
+                    se.bb_true  + this->bb_base,
+                    se.bb_false + this->bb_base
                     });
                 ),
             (Switch,
@@ -3168,9 +3168,9 @@ bool MIR_Optimise_UnifyBlocks(::MIR::TypeResolve& state, ::MIR::Function& fcn)
             (If,
                 if( ae.cond != be.cond )
                     return false;
-                if( ae.bb0 != be.bb0 )
+                if( ae.bb_true  != be.bb_true  )
                     return false;
-                if( ae.bb1 != be.bb1 )
+                if( ae.bb_false != be.bb_false )
                     return false;
                 ),
             (Switch,
@@ -4544,7 +4544,7 @@ bool MIR_Optimise_ConstPropagate(::MIR::TypeResolve& state, ::MIR::Function& fcn
                 }
                 else {
                     MIR_ASSERT(state, it->second.is_Bool(), "Terminator::If with known value not Bool - " << it->second);
-                    auto new_bb = (it->second.as_Bool().v ? te.bb0 : te.bb1);
+                    auto new_bb = (it->second.as_Bool().v ? te.bb_true : te.bb_false);
                     DEBUG(state << "Convert " << bb.terminator << " into Goto(" << new_bb << ") because condition known to be " << it->second);
                     bb.terminator = ::MIR::Terminator::make_Goto(new_bb);
 
@@ -4615,7 +4615,7 @@ bool MIR_Optimise_ConstPropagate(::MIR::TypeResolve& state, ::MIR::Function& fcn
         if( val_known )
         {
             DEBUG("bb" << bbidx << ": Condition known to be " << known_val);
-            bb.terminator = ::MIR::Terminator::make_Goto( known_val ? te.bb0 : te.bb1 );
+            bb.terminator = ::MIR::Terminator::make_Goto( known_val ? te.bb_true : te.bb_false );
             changed = true;
         }
     }
@@ -6294,8 +6294,8 @@ bool MIR_Optimise_GarbageCollect(::MIR::TypeResolve& state, ::MIR::Function& fcn
             (Panic,
                 ),
             (If,
-                e.bb0 = block_rewrite_table[e.bb0];
-                e.bb1 = block_rewrite_table[e.bb1];
+                e.bb_true  = block_rewrite_table[e.bb_true ];
+                e.bb_false = block_rewrite_table[e.bb_false];
                 ),
             (Switch,
                 for(auto& target : e.targets)
@@ -6404,8 +6404,8 @@ void MIR_SortBlocks(const StaticTraitResolve& resolve, const ::HIR::ItemPath& pa
             todo.push_back(Todo { te.dst, info.branch_count, info.level + 1 });
             ),
         (If,
-            todo.push_back(Todo { te.bb0, ++branches, info.level + 1 });
-            todo.push_back(Todo { te.bb1, ++branches, info.level + 1 });
+            todo.push_back(Todo { te.bb_true , ++branches, info.level + 1 });
+            todo.push_back(Todo { te.bb_false, ++branches, info.level + 1 });
             ),
         (Switch,
             for(auto dst : te.targets)
diff --git a/src/trans/codegen_c.cpp b/src/trans/codegen_c.cpp
index a0b1f826..98b04daa 100644
--- a/src/trans/codegen_c.cpp
+++ b/src/trans/codegen_c.cpp
@@ -2902,7 +2902,7 @@ namespace {
                     m_of << "\tgoto bb" << e << "; /* panic */\n";
                     }
                 TU_ARMA(If, e) {
-                    m_of << "\tif("; emit_lvalue(e.cond); m_of << ") goto bb" << e.bb0 << "; else goto bb" << e.bb1 << ";\n";
+                    m_of << "\tif("; emit_lvalue(e.cond); m_of << ") goto bb" << e.bb_true << "; else goto bb" << e.bb_false << ";\n";
                     }
                 TU_ARMA(Switch, e) {
 
diff --git a/src/trans/codegen_c_structured.cpp b/src/trans/codegen_c_structured.cpp
index 1d56a1ce..a2378f2d 100644
--- a/src/trans/codegen_c_structured.cpp
+++ b/src/trans/codegen_c_structured.cpp
@@ -146,34 +146,34 @@ class Converter
                 bb_idx = SIZE_MAX;
                 ),
             (If,
-                auto arm0 = process_node_ref(te.bb0);
-                auto arm1 = process_node_ref(te.bb1);
+                auto arm_t = process_node_ref(te.bb_true );
+                auto arm_f = process_node_ref(te.bb_false);
                 bb_idx = SIZE_MAX;
-                if( arm0.has_target() && arm1.has_target() ) {
-                    if( arm0.target() == arm1.target() ) {
-                        DEBUG("If targets " << arm0.target() << " == " << arm1.target());
-                        bb_idx = arm0.target();
+                if( arm_t.has_target() && arm_f.has_target() ) {
+                    if( arm_t.target() == arm_f.target() ) {
+                        DEBUG("If targets " << arm_t.target() << " == " << arm_f.target());
+                        bb_idx = arm_t.target();
                     }
                     else {
                         stop = true;
-                        DEBUG("If targets " << arm0.target() << " != " << arm1.target());
+                        DEBUG("If targets " << arm_t.target() << " != " << arm_f.target());
                         // TODO: Pick one?
                     }
                 }
-                else if( arm0.has_target() ) {
-                    DEBUG("If targets " << arm0.target() << ", NONE");
-                    bb_idx = arm0.target();
+                else if( arm_t.has_target() ) {
+                    DEBUG("If targets " << arm_t.target() << ", NONE");
+                    bb_idx = arm_t.target();
                 }
-                else if( arm1.has_target() ) {
-                    DEBUG("If targets NONE, " << arm1.target());
-                    bb_idx = arm1.target();
+                else if( arm_f.has_target() ) {
+                    DEBUG("If targets NONE, " << arm_f.target());
+                    bb_idx = arm_f.target();
                 }
                 else {
                     // No target from either arm
                     DEBUG("If targets NONE, NONE");
                     stop = true;
                 }
-                refs.push_back(Node::make_If({ bb_idx, &te.cond, mv$(arm0), mv$(arm1) }));
+                refs.push_back(Node::make_If({ bb_idx, &te.cond, mv$(arm_t), mv$(arm_f) }));
                 ),
             (Switch,
                 ::std::vector<NodeRef>  arms;
@@ -338,8 +338,8 @@ ::std::vector<Node> MIR_To_Structured(const ::MIR::Function& fcn)
         (Return,
             ),
         (If,
-            conv.m_block_ref_count[te.bb0] += 1;
-            conv.m_block_ref_count[te.bb1] += 1;
+            conv.m_block_ref_count[te.bb_true ] += 1;
+            conv.m_block_ref_count[te.bb_false] += 1;
             ),
         (Switch,
             for(auto tgt : te.targets)
diff --git a/src/trans/codegen_mmir.cpp b/src/trans/codegen_mmir.cpp
index 8ae3d975..db0d152c 100644
--- a/src/trans/codegen_mmir.cpp
+++ b/src/trans/codegen_mmir.cpp
@@ -1013,7 +1013,7 @@ namespace
                     m_of << "PANIC " << e.dst << "\n";
                     break;
                 TU_ARM(term, If, e)
-                    m_of << "IF " << fmt(e.cond) << " goto " << e.bb0 << " else " << e.bb1 << "\n";
+                    m_of << "IF " << fmt(e.cond) << " goto " << e.bb_true << " else " << e.bb_false << "\n";
                     break;
                 TU_ARM(term, Switch, e) {
                     m_of << "SWITCH " << fmt(e.val) << " { ";
diff --git a/src/trans/monomorphise.cpp b/src/trans/monomorphise.cpp
index b6063bfb..d87f7a2e 100644
--- a/src/trans/monomorphise.cpp
+++ b/src/trans/monomorphise.cpp
@@ -349,7 +349,7 @@ ::MIR::FunctionPointer Trans_Monomorphise(const ::StaticTraitResolve& resolve, c
         (If,
             terminator = ::MIR::Terminator::make_If({
                 monomorph_LValue(resolve, params, e.cond),
-                e.bb0, e.bb1
+                e.bb_true, e.bb_false
                 });
             ),
         (Switch,
diff --git a/tools/mir_opt_test/parser.cpp b/tools/mir_opt_test/parser.cpp
index 59f3f244..953785e4 100644
--- a/tools/mir_opt_test/parser.cpp
+++ b/tools/mir_opt_test/parser.cpp
@@ -941,8 +941,8 @@ namespace {
                 e.panic_block = translate_bb(e.panic_block);
                 }
             TU_ARMA(If, e) {
-                e.bb0 = translate_bb(e.bb0);
-                e.bb1 = translate_bb(e.bb1);
+                e.bb_true = translate_bb(e.bb_true);
+                e.bb_false = translate_bb(e.bb_false);
                 }
             TU_ARMA(Switch, e) {
                 for(auto& tgt : e.targets)
diff --git a/tools/standalone_miri/mir.cpp b/tools/standalone_miri/mir.cpp
index a3a91592..f4a0a19f 100644
--- a/tools/standalone_miri/mir.cpp
+++ b/tools/standalone_miri/mir.cpp
@@ -268,10 +268,10 @@ namespace MIR {
             os << "Goto(" << e << ")";
             ),
         (Panic,
-            os << "Panic(" << e.dst << ";)";
+            os << "Panic(" << e.dst << ")";
             ),
         (If,
-            os << "If( " << e.cond << " : " << e.bb0 << ", " << e.bb1 << ")";
+            os << "If( " << e.cond << " goto " << e.bb_true << " else " << e.bb_false << ")";
             ),
         (Switch,
             os << "Switch( " << e.val << " : ";
diff --git a/tools/standalone_miri/miri.cpp b/tools/standalone_miri/miri.cpp
index 6a4de893..ff9afaa2 100644
--- a/tools/standalone_miri/miri.cpp
+++ b/tools/standalone_miri/miri.cpp
@@ -1512,7 +1512,7 @@ bool InterpreterThread::step_one(Value& out_thread_result)
         TU_ARM(bb.terminator, If, te) {
             uint8_t v = state.get_value_ref(te.cond).read_u8(0);
             LOG_ASSERT(v == 0 || v == 1, "Boolean isn't 0/1 - instead " << int(v));
-            cur_frame.bb_idx = v ? te.bb0 : te.bb1;
+            cur_frame.bb_idx = v ? te.bb_true : te.bb_false;
             } break;
         TU_ARM(bb.terminator, Switch, te) {
             ::HIR::TypeRef ty;