diff --git a/lib/count-leading-zeros.h b/lib/count-leading-zeros.h
index 5904eb7..343c892 100644
--- a/lib/count-leading-zeros.h
+++ b/lib/count-leading-zeros.h
@@ -39,7 +39,22 @@ _GL_INLINE_HEADER_BEGIN
   return x ? BUILTIN (x) : CHAR_BIT * sizeof x;
 #elif _MSC_VER
 # pragma intrinsic _BitScanReverse
-# pragma intrinsic _BitScanReverse64
+# ifndef _M_IX86
+#  pragma intrinsic _BitScanReverse64
+# else
+COUNT_LEADING_ZEROS_INLINE unsigned char
+_BitScanReverse64 (unsigned long *r, unsigned __int64 x)
+{
+  unsigned char c = _BitScanReverse (r, x >> 32);
+  if (! c)
+    {
+      c = _BitScanReverse (r, x);
+      if (c)
+        *r += 32;
+    }
+  return c;
+}
+# endif
 # define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE)                \
     do                                                                  \
       {                                                                 \
diff --git a/lib/count-trailing-zeros.h b/lib/count-trailing-zeros.h
index 83ce2fb..39b879f 100644
--- a/lib/count-trailing-zeros.h
+++ b/lib/count-trailing-zeros.h
@@ -39,7 +39,21 @@ _GL_INLINE_HEADER_BEGIN
   return x ? BUILTIN (x) : CHAR_BIT * sizeof x;
 #elif _MSC_VER
 # pragma intrinsic _BitScanForward
-# pragma intrinsic _BitScanForward64
+# ifndef _M_IX86
+#  pragma intrinsic _BitScanForward64
+# else
+COUNT_TRAILING_ZEROS_INLINE unsigned char
+_BitScanForward64 (unsigned long *r, unsigned __int64 x)
+{
+  unsigned char c = _BitScanForward (r, x);
+  if (! c)
+    {
+      c = _BitScanForward (r, x >> 32);
+      if (c)
+        *r += 32;
+    }
+  return c;
+}
 # define COUNT_TRAILING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE)               \
     do                                                                  \
       {                                                                 \