diff --git a/log.h b/log.h
index 6dcb0b8d..1be82cb5 100644
--- a/log.h
+++ b/log.h
@@ -25,7 +25,7 @@
 #define REPMGR_SYSLOG 1
 #define REPMGR_STDERR 2
 
-void stderr_log_with_level(const char *level_name, int level, const char *fmt, ...);
+void stderr_log_with_level(const char *level_name, int level, const char *fmt, ...) __attribute__ ((format (PG_PRINTF_ATTRIBUTE, 3, 4)));
 
 /* Standard error logging */
 #define stderr_log_debug(...) stderr_log_with_level("DEBUG", LOG_DEBUG, __VA_ARGS__)
diff --git a/strutil.c b/strutil.c
index aaa186d3..fb14cb7e 100644
--- a/strutil.c
+++ b/strutil.c
@@ -25,7 +25,7 @@
 #include "log.h"
 #include "strutil.h"
 
-static int xvsnprintf(char *str, size_t size, const char *format, va_list ap);
+static int xvsnprintf(char *str, size_t size, const char *format, va_list ap) __attribute__ ((format (PG_PRINTF_ATTRIBUTE, 3, 0)));
 
 /* Add strnlen on platforms that don't have it, like OS X */
 #ifndef strnlen
diff --git a/strutil.h b/strutil.h
index 75eb63a4..cb3ee45e 100644
--- a/strutil.h
+++ b/strutil.h
@@ -31,9 +31,9 @@
 #define MAXCONNINFO		1024
 
 
-extern int xsnprintf(char *str, size_t size, const char *format, ...);
-extern int sqlquery_snprintf(char *str, const char *format, ...);
-extern int maxlen_snprintf(char *str, const char *format, ...);
+extern int xsnprintf(char *str, size_t size, const char *format, ...) __attribute__ ((format (PG_PRINTF_ATTRIBUTE, 3, 4)));
+extern int sqlquery_snprintf(char *str, const char *format, ...) __attribute__ ((format (PG_PRINTF_ATTRIBUTE, 2, 3)));
+extern int maxlen_snprintf(char *str, const char *format, ...) __attribute__ ((format (PG_PRINTF_ATTRIBUTE, 2, 3)));
 
 /* Add strnlen on platforms that don't have it, like OS X */
 #ifndef strnlen