diff --git a/source/duke3d/src/gameexec.cpp b/source/duke3d/src/gameexec.cpp
index 4f78523fc..bce69211a 100644
--- a/source/duke3d/src/gameexec.cpp
+++ b/source/duke3d/src/gameexec.cpp
@@ -499,7 +499,7 @@ void A_Fall(int const spriteNum)
         }
 }
 
-int G_GetAngleDelta(int currAngle, int newAngle)
+int32_t __fastcall G_GetAngleDelta(int32_t currAngle, int32_t newAngle)
 {
     currAngle &= 2047;
     newAngle &= 2047;
diff --git a/source/duke3d/src/gameexec.h b/source/duke3d/src/gameexec.h
index bcfd48d64..67f653245 100644
--- a/source/duke3d/src/gameexec.h
+++ b/source/duke3d/src/gameexec.h
@@ -51,7 +51,7 @@ void A_Execute(int spriteNum, int playerNum, int playerDist);
 void A_Fall(int const spriteNum);
 int32_t A_GetFurthestAngle(int const spriteNum, int const angDiv);
 void A_GetZLimits(int const spriteNum);
-int G_GetAngleDelta(int a, int na);
+int32_t __fastcall G_GetAngleDelta(int32_t currAngle, int32_t newAngle);
 void G_RestoreMapState();
 void G_SaveMapState();