diff --git a/icu4c/source/common/unicode/platform.h.in b/icu4c/source/common/unicode/platform.h.in
index 75230e08ce9..543f5aef00e 100644
--- a/icu4c/source/common/unicode/platform.h.in
+++ b/icu4c/source/common/unicode/platform.h.in
@@ -170,7 +170,7 @@ typedef unsigned int uint32_t;
 #define ICU_USE_THREADS @ICU_USE_THREADS@
 
 /* On strong memory model CPUs (e.g. x86 CPUs), we use a safe & quick double check lock. */
-#if defined(__GNUC__) && (defined(__i386__) || defined(__amd64__))
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
 #define UMTX_STRONG_MEMORY_MODEL 1
 #endif