diff --git a/SPIRV/GlslangToSpv.cpp b/SPIRV/GlslangToSpv.cpp
index e5e2169..00369d2 100755
--- a/SPIRV/GlslangToSpv.cpp
+++ b/SPIRV/GlslangToSpv.cpp
@@ -1342,19 +1342,17 @@
 bool TGlslangToSpvTraverser::visitLoop(glslang::TVisit /* visit */, glslang::TIntermLoop* node)
 {
     auto blocks = builder.makeNewLoop();
+    builder.createBranch(&blocks.head);
     if (node->testFirst() && node->getTest()) {
-        spv::Block& head = builder.makeNewBlock();
-        builder.createBranch(&head);
-
-        builder.setBuildPoint(&head);
+        builder.setBuildPoint(&blocks.head);
         node->getTest()->traverse(this);
         spv::Id condition =
             builder.accessChainLoad(convertGlslangToSpvType(node->getTest()->getType()));
         builder.createLoopMerge(&blocks.merge, &blocks.continue_target, spv::LoopControlMaskNone);
         builder.createConditionalBranch(condition, &blocks.body, &blocks.merge);
 
-        breakForLoop.push(true);
         builder.setBuildPoint(&blocks.body);
+        breakForLoop.push(true);
         if (node->getBody())
             node->getBody()->traverse(this);
         builder.createBranch(&blocks.continue_target);
@@ -1363,8 +1361,14 @@
         builder.setBuildPoint(&blocks.continue_target);
         if (node->getTerminal())
             node->getTerminal()->traverse(this);
-        builder.createBranch(&head);
+        builder.createBranch(&blocks.head);
     } else {
+        // Spec requires back edges to target header blocks, and every header
+        // block must dominate its merge block.  Create an empty header block
+        // here to ensure these conditions are met even when body contains
+        // non-trivial control flow.
+        builder.setBuildPoint(&blocks.head);
+        builder.createLoopMerge(&blocks.merge, &blocks.continue_target, spv::LoopControlMaskNone);
         builder.createBranch(&blocks.body);
 
         breakForLoop.push(true);
@@ -1381,14 +1385,17 @@
             node->getTest()->traverse(this);
             spv::Id condition =
                 builder.accessChainLoad(convertGlslangToSpvType(node->getTest()->getType()));
-            builder.createLoopMerge(&blocks.merge, &blocks.continue_target,
-                                    spv::LoopControlMaskNone);
-            builder.createConditionalBranch(condition, &blocks.body, &blocks.merge);
+            builder.createConditionalBranch(condition, &blocks.head, &blocks.merge);
         } else {
-            builder.createBranch(&blocks.body);
+            // TODO: unless there was a break instruction somewhere in the body,
+            // this is an infinite loop, so we should abort code generation with
+            // a warning.  As it stands now, nothing will jump to the merge
+            // block, and it may be dropped as unreachable by the SPIR-V dumper.
+            // That, in turn, will result in a non-existing %ID in the LoopMerge
+            // above.
+            builder.createBranch(&blocks.head);
         }
     }
-
     builder.setBuildPoint(&blocks.merge);
     builder.closeLoop();
     return false;