diff --git a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/CloudFunctionObject/CloudFunctionObject.H b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/CloudFunctionObject/CloudFunctionObject.H
index 5baf0f7ae9..5130660885 100644
--- a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/CloudFunctionObject/CloudFunctionObject.H
+++ b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/CloudFunctionObject/CloudFunctionObject.H
@@ -46,6 +46,9 @@ SourceFiles
 namespace Foam
 {
 
+class polyPatch;
+class tetIndices;
+
 /*---------------------------------------------------------------------------*\
                     Class CloudFunctionObject Declaration
 \*---------------------------------------------------------------------------*/