diff --git a/mesonbuild/compilers/swift.py b/mesonbuild/compilers/swift.py
index 66460c0c6537..a867c7ceda75 100644
--- a/mesonbuild/compilers/swift.py
+++ b/mesonbuild/compilers/swift.py
@@ -24,7 +24,7 @@
     '1': ['-O'],
     '2': ['-O'],
     '3': ['-O'],
-    's': ['-O'],
+    's': ['-Osize'],
 }
 
 class SwiftCompiler(Compiler):