diff --git a/js/js.libraries/src/generated/org.w3c.dom.kt b/js/js.libraries/src/generated/org.w3c.dom.kt
index 7c7100fce61..05e2896865d 100644
--- a/js/js.libraries/src/generated/org.w3c.dom.kt
+++ b/js/js.libraries/src/generated/org.w3c.dom.kt
@@ -290,7 +290,7 @@ native public open class Document : Node {
     var onended: ((Event) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
-    var onerror: ((dynamic,dynamic,String,Int,Int,dynamic) -> dynamic)?
+    var onerror: ((dynamic, dynamic, String, Int, Int, dynamic) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
     var onfocus: ((Event) -> dynamic)?
@@ -623,7 +623,7 @@ native public trait HTMLElement : Element {
     var onended: ((Event) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
-    var onerror: ((dynamic,dynamic,String,Int,Int,dynamic) -> dynamic)?
+    var onerror: ((dynamic, dynamic, String, Int, Int, dynamic) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
     var onfocus: ((Event) -> dynamic)?
@@ -3170,7 +3170,7 @@ native public trait Window : EventTarget {
     var onended: ((Event) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
-    var onerror: ((dynamic,dynamic,String,Int,Int,dynamic) -> dynamic)?
+    var onerror: ((dynamic, dynamic, String, Int, Int, dynamic) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
     var onfocus: ((Event) -> dynamic)?
@@ -3796,7 +3796,7 @@ native public trait WorkerGlobalScope : EventTarget {
     var location: WorkerLocation
         get() = noImpl
         set(value) = noImpl
-    var onerror: ((dynamic,dynamic,String,Int,Int,dynamic) -> dynamic)?
+    var onerror: ((dynamic, dynamic, String, Int, Int, dynamic) -> dynamic)?
         get() = noImpl
         set(value) = noImpl
     var onlanguagechange: ((Event) -> dynamic)?
@@ -4279,7 +4279,7 @@ native public trait HTMLCollection : UnionElementOrHTMLCollection {
     nativeGetter fun get(name: String): Element? = noImpl
 }
 
-native public open class MutationObserver(callback: (Array<MutationRecord>,MutationObserver) -> Unit) {
+native public open class MutationObserver(callback: (Array<MutationRecord>, MutationObserver) -> Unit) {
     fun observe(target: Node, options: MutationObserverInit): Unit = noImpl
     fun disconnect(): Unit = noImpl
     fun takeRecords(): Array<MutationRecord> = noImpl
diff --git a/libraries/tools/idl2k/src/main/kotlin/gen.kt b/libraries/tools/idl2k/src/main/kotlin/gen.kt
index 1e63a20f1b7..6c64346327f 100644
--- a/libraries/tools/idl2k/src/main/kotlin/gen.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/gen.kt
@@ -67,7 +67,7 @@ fun generateFunctions(repository: Repository, function: Operation): List<Generat
                 it.copy(type = callbackFunction.parameters
                         .map { it.copy(type = mapType(repository, it.type)) }
                         .map { it.formatFunctionTypePart() }
-                        .join(",", "(", ") -> ${mapType(repository, callbackFunction.returnType)}")
+                        .join(", ", "(", ") -> ${mapType(repository, callbackFunction.returnType)}")
                         .copyNullabilityFrom(it.type))
             }
             else -> it
diff --git a/libraries/tools/idl2k/src/main/kotlin/idl.kt b/libraries/tools/idl2k/src/main/kotlin/idl.kt
index 789fecc37cb..f72ff0ffbc7 100644
--- a/libraries/tools/idl2k/src/main/kotlin/idl.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/idl.kt
@@ -290,7 +290,7 @@ class DefinitionVisitor(val extendedAttributes: List<ExtendedAttribute>, val nam
         name = getName(ctx)
 
         val function = OperationVisitor(memberAttributes.toList()).visit(ctx)
-        typedefType = "(${function.parameters.map { it.formatFunctionTypePart() }.join(",")}) -> ${function.returnType}"
+        typedefType = "(${function.parameters.map { it.formatFunctionTypePart() }.join(", ")}) -> ${function.returnType}"
 
         memberAttributes.clear()
         return defaultResult()
diff --git a/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt b/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
index f39fe5e9ac8..cdd66c721b7 100644
--- a/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
+++ b/libraries/tools/idl2k/src/main/kotlin/typeMappings.kt
@@ -60,7 +60,7 @@ data class FunctionType(val parameterTypes : List<Attribute>, val returnType : S
 val FunctionType.arity : Int
     get() = parameterTypes.size()
 val FunctionType.text : String
-    get() = "(${parameterTypes.map { it.formatFunctionTypePart() }.join(",")}) -> ${returnType}"
+    get() = "(${parameterTypes.map { it.formatFunctionTypePart() }.join(", ")}) -> ${returnType}"
 
 fun FunctionType(text : String) : FunctionType {
     val (parameters, returnType) = text.split("->".toRegex()).map { it.trim() }.filter { it != "" }