diff --git a/GNUmakefile b/GNUmakefile
index ae38c0a7..b9a9d0b6 100755
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -668,7 +668,6 @@ ifeq ($(DETECT_FEATURES),1)
     BLAKE2S_FLAG = $(POWER7_FLAG)
     CHACHA_FLAG = $(POWER7_FLAG)
     CHAM_FLAG = $(POWER7_FLAG)
-    GCM_FLAG = $(POWER7_FLAG)
     LEA_FLAG = $(POWER7_FLAG)
     SIMECK_FLAG = $(POWER7_FLAG)
     SIMON64_FLAG = $(POWER7_FLAG)
@@ -704,6 +703,11 @@ ifeq ($(DETECT_FEATURES),1)
     POWER4_FLAG =
   endif
 
+  # Drop GCM to Power7 if Power8 is not available.
+  ifeq ($(POWER8_FLAG),)
+    GCM_FLAG = $(POWER7_FLAG)
+  endif
+
   # Drop SIMON64 and SPECK64 to Power4 if Power7 not available
   ifeq ($(SIMON64_FLAG)$(SPECK64_FLAG)$(ALTIVEC_FLAG),$(ALTIVEC_FLAG))
     SIMON64_FLAG = $(ALTIVEC_FLAG)