diff --git a/Makefile b/Makefile
index 76ebef0..a0f0f0c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,12 +1,14 @@
 basic_flags := -std=c99 -pipe -Wall -Wpedantic -Wextra -Werror=implicit-function-declaration -D_XOPEN_SOURCE_EXTENDED=1
-debug_flags := -DDEBUG -Og -ggdb -feliminate-unused-debug-symbols
+debug_flags := -DDEBUG -ggdb
 sanitize_flags := -fsanitize=address -fsanitize=undefined
 # note: -fsanitize=leak not available on at least Mac 10.12
 release_flags := -DNDEBUG -O2 -s -D_FORTIFY_SOURCE=2 -fstack-protector-strong -fpie -Wl,-pie
 cli_library_flags :=
 ifeq ($(shell uname -s), Darwin)
+debug_flags := $(debug_flags) -O1
 tui_library_flags := -lncurses
 else
+debug_flags := $(debug_flags) -Og -feliminate-unused-debug-symbols
 tui_library_flags := -lncursesw
 endif
 common_source_files := field.c sim.c
diff --git a/field.c b/field.c
index 9c497e9..4c2afeb 100644
--- a/field.c
+++ b/field.c
@@ -141,7 +141,7 @@ void field_poke_relative(Field* f, U32 y, U32 x, I32 offs_y, I32 offs_x,
   f->buffer[y0 * f_width + x0] = term;
 }
 
-inline bool term_char_is_valid(char c) {
+static inline bool term_char_is_valid(char c) {
   return c >= '#' && c <= '~';
 }