diff --git a/src/common.h b/src/common.h
index 7c92f85f2c..ac7a4e6c21 100644
--- a/src/common.h
+++ b/src/common.h
@@ -260,6 +260,18 @@ pad(unsigned n)
   return pad(n, BytesPerWord);
 }
 
+inline uintptr_t
+padWord(uintptr_t n, uintptr_t alignment)
+{
+  return (n + (alignment - 1)) & ~(alignment - 1);
+}
+
+inline uintptr_t
+padWord(uintptr_t n)
+{
+  return padWord(n, BytesPerWord);
+}
+
 inline unsigned
 ceiling(unsigned n, unsigned d)
 {
diff --git a/src/compile.cpp b/src/compile.cpp
index a3a93fb8c0..e123bac0ed 100644
--- a/src/compile.cpp
+++ b/src/compile.cpp
@@ -7694,7 +7694,7 @@ boot(MyThread* t, BootImage* image)
   unsigned* callTable = stringTable + image->stringCount;
 
   uintptr_t* heapMap = reinterpret_cast<uintptr_t*>
-    (pad(reinterpret_cast<uintptr_t>(callTable + (image->callCount * 2))));
+    (padWord(reinterpret_cast<uintptr_t>(callTable + (image->callCount * 2))));
   unsigned heapMapSizeInWords = ceiling
     (heapMapSize(image->heapSize), BytesPerWord);
   uintptr_t* heap = heapMap + heapMapSizeInWords;