diff --git a/dive.c b/dive.c
index 6f9f4a922..405812271 100644
--- a/dive.c
+++ b/dive.c
@@ -123,7 +123,7 @@ unsigned int units_to_depth(double depth)
 	return feet_to_mm(depth);
 }
 
-double get_depth_units(unsigned int mm, int *frac, const char **units)
+double get_depth_units(int mm, int *frac, const char **units)
 {
 	int decimals;
 	double d;
diff --git a/dive.h b/dive.h
index 9cc55c964..abbf4a7ae 100644
--- a/dive.h
+++ b/dive.h
@@ -152,7 +152,7 @@ typedef struct
 } weightsystem_t;
 
 extern int get_pressure_units(unsigned int mb, const char **units);
-extern double get_depth_units(unsigned int mm, int *frac, const char **units);
+extern double get_depth_units(int mm, int *frac, const char **units);
 extern double get_volume_units(unsigned int ml, int *frac, const char **units);
 extern double get_temp_units(unsigned int mk, const char **units);
 extern double get_weight_units(unsigned int grams, int *frac, const char **units);