diff --git a/CMakeLists.txt b/CMakeLists.txt
index ad17fbf..a5e8c1c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,6 +18,7 @@ option(USE_GETTEXT "Enable interantionalization" OFF)
 add_compile_options(-Wall -pedantic -Wextra)
 add_compile_options(-Werror=unused-label)
 add_compile_options(-Werror=unused-parameter)
+add_compile_options(-Werror=strict-prototypes)
 
 set(SOURCES
   colors.c
diff --git a/error.c b/error.c
index ac41849..6fd11ef 100644
--- a/error.c
+++ b/error.c
@@ -45,12 +45,12 @@ void set_error(const char *fmt, ...)
 	va_end(ap);
 }
 
-void clear_error()
+void clear_error(void)
 {
 	last_error[0] = 0x00;
 }
 
-char * get_error()
+char * get_error(void)
 {
 	return last_error;
 }
diff --git a/nc.c b/nc.c
index 3c92196..80f8812 100644
--- a/nc.c
+++ b/nc.c
@@ -463,7 +463,7 @@ void draw_rad_column(WINDOW *win, int x, double val)
 	}
 }
 
-double get_cur_scc()
+double get_cur_scc(void)
 {
         double scc_val = 0.0;
         double prev_val = 0.0, u0 = 0.0;
@@ -593,7 +593,7 @@ void draw_fft(void)
 }
 #endif
 
-double calc_trend()
+double calc_trend(void)
 {
 	int half = history_n / 2, index = 0;
 	double v1 = 0.0, v2 = 0.0;
@@ -626,7 +626,7 @@ double calc_trend()
 	return (v1 - v2) / (v2 / 100.0);
 }
 
-void draw_graph()
+void draw_graph(void)
 {
 	int index = 0, loop_n = min(max_x, history_n), n = 0, n2 = 0;
 	double avg = 0, sd = 0;