diff --git a/gegl/source/lib.rs b/gegl/source/lib.rs
index 672eba0..705f5cd 100644
--- a/gegl/source/lib.rs
+++ b/gegl/source/lib.rs
@@ -31,6 +31,7 @@ pub trait GeglOperation: Default + std::fmt::Debug {
         continue;
       }
 
+      let key = key.replace('_', "-");
       graph.push(format!("{key}={value}"));
     }
 
diff --git a/gegl/tests/snapshots/bloom__graphs.snap b/gegl/tests/snapshots/bloom__graphs.snap
index d3972cc..89fa101 100644
--- a/gegl/tests/snapshots/bloom__graphs.snap
+++ b/gegl/tests/snapshots/bloom__graphs.snap
@@ -7,7 +7,7 @@ expression: graphs
         "non-default: exclude defaults",
         [
             "gegl:bloom",
-            "limit_exposure=true",
+            "limit-exposure=true",
             "radius=100",
             "softness=100",
         ],
@@ -16,7 +16,7 @@ expression: graphs
         "non-default: include defaults",
         [
             "gegl:bloom",
-            "limit_exposure=true",
+            "limit-exposure=true",
             "radius=100",
             "softness=100",
             "strength=50",
@@ -33,7 +33,7 @@ expression: graphs
         "default: include defaults",
         [
             "gegl:bloom",
-            "limit_exposure=false",
+            "limit-exposure=false",
             "radius=10",
             "softness=25",
             "strength=50",
diff --git a/gegl/tests/snapshots/cartoon__graphs.snap b/gegl/tests/snapshots/cartoon__graphs.snap
index 3040ce7..b70f941 100644
--- a/gegl/tests/snapshots/cartoon__graphs.snap
+++ b/gegl/tests/snapshots/cartoon__graphs.snap
@@ -7,15 +7,15 @@ expression: graphs
         "non-default: exclude defaults",
         [
             "gegl:cartoon",
-            "mask_radius=0.1",
+            "mask-radius=0.1",
         ],
     ),
     (
         "non-default: include defaults",
         [
             "gegl:cartoon",
-            "mask_radius=0.1",
-            "pct_black=0.2",
+            "mask-radius=0.1",
+            "pct-black=0.2",
         ],
     ),
     (
@@ -28,8 +28,8 @@ expression: graphs
         "default: include defaults",
         [
             "gegl:cartoon",
-            "mask_radius=7",
-            "pct_black=0.2",
+            "mask-radius=7",
+            "pct-black=0.2",
         ],
     ),
 ]