diff --git a/inputfiles/overridingTypes.jsonc b/inputfiles/overridingTypes.jsonc
index 32683a28b..60e7c5823 100644
--- a/inputfiles/overridingTypes.jsonc
+++ b/inputfiles/overridingTypes.jsonc
@@ -30,25 +30,6 @@
                     }
                 }
             },
-            "WebGLRenderingContextBase": {
-                "methods": {
-                    "method": {
-                        "pixelStorei": {
-                            "name": "pixelStorei",
-                            "signature": {
-                                "0": {
-                                    "param": [
-                                        {
-                                            "name": "param",
-                                            "additionalTypes": ["GLboolean"]
-                                        }
-                                    ]
-                                }
-                            }
-                        }
-                    }
-                }
-            },
             "Body": {
                 "properties": {
                     "property": {
@@ -1419,18 +1400,6 @@
             "SubtleCrypto": {
                 "methods": {
                     "method": {
-                        "decrypt": {
-                            "signature": {
-                                "0": {
-                                    "param": [
-                                        {
-                                            "name": "algorithm",
-                                            "additionalTypes": ["RsaOaepParams", "AesCtrParams", "AesCbcParams", "AesGcmParams"]
-                                        }
-                                    ]
-                                }
-                            }
-                        },
                         "deriveBits": {
                             "signature": {
                                 "0": {
diff --git a/inputfiles/patches/webcrypto.kdl b/inputfiles/patches/webcrypto.kdl
index db6844f2a..42ef5bc73 100644
--- a/inputfiles/patches/webcrypto.kdl
+++ b/inputfiles/patches/webcrypto.kdl
@@ -13,6 +13,14 @@ interface CryptoKey {
   }
 }
 
+interface SubtleCrypto {
+  method decrypt signatureIndex=0 {
+    param algorithm {
+      additionalTypes RsaOaepParams AesCtrParams AesCbcParams AesGcmParams
+    }
+  }
+}
+
 removals {
   enum KeyFormat {
     raw-private // No implementation as of 2025-09
diff --git a/inputfiles/patches/webgl.kdl b/inputfiles/patches/webgl.kdl
index 3d314d954..645153230 100644
--- a/inputfiles/patches/webgl.kdl
+++ b/inputfiles/patches/webgl.kdl
@@ -170,4 +170,10 @@ interface-mixin WebGLRenderingContextBase {
     param extensionName overrideType="\"WEBGL_multi_draw\""
     type WEBGL_multi_draw nullable=#true
   }
+
+  method pixelStorei signatureIndex=0 {
+    param param {
+      additionalTypes GLboolean
+    }
+  }
 }
diff --git a/src/build/patches.ts b/src/build/patches.ts
index 0bf053af7..f14fa625d 100644
--- a/src/build/patches.ts
+++ b/src/build/patches.ts
@@ -262,6 +262,32 @@ function handleProperty(child: Node): Partial<Property> {
   };
 }
 
+function handleParam(node: Node) {
+  const name = string(node.values[0]);
+  let additionalTypes: string[] | undefined;
+
+  for (const child of node.children) {
+    switch (child.name) {
+      case "additionalTypes": {
+        if (additionalTypes) {
+          throw new Error("Unexpected multiple additionalTypes node");
+        }
+        additionalTypes = child.values.map(string);
+        break;
+      }
+      default:
+        throw new Error(`Unexpected child "${child.name}" in param "${name}"`);
+    }
+  }
+
+  return {
+    name,
+    ...optionalMember("type", "string", node.properties?.type),
+    ...optionalMember("overrideType", "string", node.properties?.overrideType),
+    additionalTypes,
+  };
+}
+
 /**
  * Handles a child node of type "method" and adds it to the method object.
  * @param child The child node to handle.
@@ -282,15 +308,7 @@ function handleMethod(child: Node): DeepPartial<OverridableMethod> {
         break;
 
       case "param":
-        params.push({
-          name: string(c.values[0]),
-          ...optionalMember("type", "string", c.properties?.type),
-          ...optionalMember(
-            "overrideType",
-            "string",
-            c.properties?.overrideType,
-          ),
-        });
+        params.push(handleParam(c));
         break;
 
       default:
@@ -308,12 +326,9 @@ function handleMethod(child: Node): DeepPartial<OverridableMethod> {
       : null;
 
   const signatureIndex = child.properties?.signatureIndex;
-  if ((params.length || signatureIndex) && !type) {
-    throw new Error("A method signature requires a type");
-  }
 
   let signature: OverridableMethod["signature"] = [];
-  if (type) {
+  if (type || params.length > 0) {
     // Determine the actual signature object
     const signatureObj: DeepPartial<Signature> = {
       param: params,