diff --git a/Makefile.ac b/Makefile.ac
index 7fd56cd35a..9939768bcd 100644
--- a/Makefile.ac
+++ b/Makefile.ac
@@ -65,7 +65,7 @@ Q=@
 ifeq ($(MAKECMDGOALS),all_ac_h)
 -include $(MAKEFILE_AC)
 
-ifdef PERIODIC_FREQUENC
+ifdef PERIODIC_FREQUENCY
 # telemetry and module periodic frequency default to PERIODIC_FREQUENCY
 TELEMETRY_FREQUENCY ?= $(PERIODIC_FREQUENCY)
 DEFAULT_MODULES_FREQUENCY = $(PERIODIC_FREQUENCY)