diff --git a/src/emu/validity.cpp b/src/emu/validity.cpp
index a7e87c39f12..ff29b1b7442 100644
--- a/src/emu/validity.cpp
+++ b/src/emu/validity.cpp
@@ -514,9 +514,13 @@ void validity_checker::validate_inlines()
 	testi32a = (testi32a & 0x0000ffff) | 0x400000;
 	if (count_leading_zeros(testi32a) != 9)
 		osd_printf_error("Error testing count_leading_zeros\n");
+	if (count_leading_zeros(0) != 32)
+		osd_printf_error("Error testing count_leading_zeros\n");
 	testi32a = (testi32a | 0xffff0000) & ~0x400000;
 	if (count_leading_ones(testi32a) != 9)
 		osd_printf_error("Error testing count_leading_ones\n");
+	if (count_leading_ones(0xffffffff) != 32)
+		osd_printf_error("Error testing count_leading_ones\n");
 }
 
 
diff --git a/src/osd/eigccx86.h b/src/osd/eigccx86.h
index b67b646451e..b3831d21524 100644
--- a/src/osd/eigccx86.h
+++ b/src/osd/eigccx86.h
@@ -474,13 +474,12 @@ _count_leading_zeros(uint32_t value)
 	__asm__ (
 		" bsrl    %[value], %[result] ;"
 		" cmovzl  %[bias], %[result]  ;"
-		" xorl    $31, %[result]      ;"
 		: [result] "=&r" (result)       // result can be in any register
 		: [value]  "rm"  (value)        // 'value' can be register or memory
-		, [bias]   "rm"  (uint32_t(63)) // 'bias' can be register or memory
+		, [bias]   "rm"  (~uint32_t(0)) // 'bias' can be register or memory
 		: "cc"                          // clobbers condition codes
 	);
-	return result;
+	return 31U - result;
 }
 
 
@@ -497,13 +496,12 @@ _count_leading_ones(uint32_t value)
 	__asm__ (
 		" bsrl    %[value], %[result] ;"
 		" cmovzl  %[bias], %[result]  ;"
-		" xorl    $31, %[result]      ;"
 		: [result] "=&r" (result)       // result can be in any register
 		: [value]  "rm"  (~value)       // 'value' can be register or memory
-		, [bias]   "rm"  (uint32_t(63)) // 'bias' can be register or memory
+		, [bias]   "rm"  (~uint32_t(0)) // 'bias' can be register or memory
 		: "cc"                          // clobbers condition codes
 	);
-	return result;
+	return 31U - result;
 }
 
 #endif // MAME_OSD_EIGCCX86_H
diff --git a/src/osd/eivc.h b/src/osd/eivc.h
index de4ea809a28..3fa34f51b3c 100644
--- a/src/osd/eivc.h
+++ b/src/osd/eivc.h
@@ -31,7 +31,7 @@
 inline uint8_t _count_leading_zeros(uint32_t value)
 {
 	unsigned long index;
-	return _BitScanReverse(&index, value) ? (index ^ 31) : 32;
+	return _BitScanReverse(&index, value) ? (31U - index) : 32U;
 }
 #endif
 
@@ -46,7 +46,7 @@ inline uint8_t _count_leading_zeros(uint32_t value)
 inline uint8_t _count_leading_ones(uint32_t value)
 {
 	unsigned long index;
-	return _BitScanReverse(&index, ~value) ? (index ^ 31) : 32;
+	return _BitScanReverse(&index, ~value) ? (31U - index) : 32U;
 }
 #endif