diff --git a/library/src/main/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistration.scala b/library/src/main/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistration.scala
index aded15d..79d0073 100644
--- a/library/src/main/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistration.scala
+++ b/library/src/main/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistration.scala
@@ -77,13 +77,13 @@ class OpenAPIModelRegistration(
     else
       tpe.dealias match {
         case t if tpe.typeSymbol.isClass && tpe.typeSymbol.asClass.isCaseClass => handleCaseType(t)
-        case t if t <:< typeOf[Map[_, _]]                                      => handleMap(t)
-        case t if t <:< typeOf[Option[_]]                                      => handleType(t.typeArgs.head)
-        case t if t <:< typeOf[Seq[_]] || t <:< typeOf[Array[_]]               => handleSeqLike(t)
-        case t if t <:< typeOf[Set[_]]                                         => handleSet(t)
-        case t if t <:< typeOf[Enumeration#Value]                              => handleEnum(t)
-        case t if t.typeSymbol.isClass && t.typeSymbol.asClass.isSealed        => handleSealedType(t)
-        case t                                                                 => handleSimpleType(t)
+        case t if t <:< typeOf[Map[_, _]]                               => handleMap(t.typeArgs(0), t.typeArgs(1))
+        case t if t <:< typeOf[Option[_]]                               => handleType(t.typeArgs.head)
+        case t if t <:< typeOf[Seq[_]] || t <:< typeOf[Array[_]]        => handleSeqLike(t)
+        case t if t <:< typeOf[Set[_]]                                  => handleSet(t)
+        case t if t <:< typeOf[Enumeration#Value]                       => handleEnum(t)
+        case t if t.typeSymbol.isClass && t.typeSymbol.asClass.isSealed => handleSealedType(t)
+        case t                                                          => handleSimpleType(t)
       }
   }
 
@@ -112,10 +112,13 @@ class OpenAPIModelRegistration(
     registerAsReference(name, schema)
   }
 
-  private def handleMap(tpe: Type): Schema[_] = {
-    val schema = new Schema
-    schema.setType("object")
-    schema
+  private def handleMap(keyType: Type, valueType: Type): Schema[_] = keyType match {
+    case _ if keyType <:< typeOf[String] =>
+      val schema = new Schema
+      schema.setType("object")
+      schema.setAdditionalProperties(handleType(valueType))
+      schema
+    case _ => throw new IllegalArgumentException("In OpenAPI 3.0.x Map must have String key type.")
   }
 
   private def handleSeqLike(tpe: Type): Schema[_] = {
diff --git a/library/src/test/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistrationSpec.scala b/library/src/test/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistrationSpec.scala
index 11ff79b..038ca8d 100644
--- a/library/src/test/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistrationSpec.scala
+++ b/library/src/test/scala/za/co/absa/springdocopenapiscala/OpenAPIModelRegistrationSpec.scala
@@ -80,7 +80,12 @@ class OpenAPIModelRegistrationSpec extends AnyFlatSpec {
 
   private case class Maps(
     a: Map[String, Int],
-    b: Map[Int, Arrays]
+    b: Map[String, Arrays]
+  )
+
+  private case class WrongMaps(
+    a: Map[Int, Int],
+    b: Map[Boolean, Arrays]
   )
 
   private object Things extends Enumeration {
@@ -262,7 +267,7 @@ class OpenAPIModelRegistrationSpec extends AnyFlatSpec {
     assertIsArrayOfExpectedType(actualSchemas, "Arrays.h", "integer")
   }
 
-  it should "make Map an OpenAPI object type" in {
+  it should "make Map an OpenAPI object type with value schema as additionalProperties" in {
     val components = new Components
     val openAPIModelRegistration = new OpenAPIModelRegistration(components)
 
@@ -271,7 +276,26 @@ class OpenAPIModelRegistrationSpec extends AnyFlatSpec {
     val actualSchemas = components.getSchemas
 
     assertTypeAndFormatAreAsExpected(actualSchemas, "Maps.a", "object")
+    assertAdditionalPropertiesAreAsExpected(
+      actualSchemas,
+      "Maps.a",
+      (new Schema).`type`("integer").format("int32")
+    )
     assertTypeAndFormatAreAsExpected(actualSchemas, "Maps.b", "object")
+    assertAdditionalPropertiesAreAsExpected(
+      actualSchemas,
+      "Maps.b",
+      (new Schema).$ref("#/components/schemas/Arrays")
+    )
+  }
+
+  it should "throw IllegalArgumentException if Map has key type different than String" in {
+    val components = new Components
+    val openAPIModelRegistration = new OpenAPIModelRegistration(components)
+
+    intercept[IllegalArgumentException] {
+      openAPIModelRegistration.register[WrongMaps]()
+    }
   }
 
   it should "make simple Enumeration (without renaming) an OpenAPI enum" in {
@@ -805,6 +829,16 @@ class OpenAPIModelRegistrationSpec extends AnyFlatSpec {
     schema => schema.getType === expectedType && Option(schema.getFormat) === expectedFormat
   )
 
+  private def assertAdditionalPropertiesAreAsExpected(
+    actualSchemas: java.util.Map[String, Schema[_]],
+    fieldPath: String,
+    expectedAdditionalProperties: AnyRef
+  ): scalatest.Assertion = assertPredicateForPath(
+    actualSchemas,
+    fieldPath,
+    schema => Option(schema.getAdditionalProperties).map(_ === expectedAdditionalProperties).getOrElse(false)
+  )
+
   private def assertRefIsAsExpected(
     actualSchemas: java.util.Map[String, Schema[_]],
     fieldPath: String,