diff --git a/src/gs-entbase/shared/NSSurfacePropEntity.qc b/src/gs-entbase/shared/NSSurfacePropEntity.qc
index 19f679c1..fb758985 100644
--- a/src/gs-entbase/shared/NSSurfacePropEntity.qc
+++ b/src/gs-entbase/shared/NSSurfacePropEntity.qc
@@ -257,13 +257,21 @@ void
 NSSurfacePropEntity::SurfaceDataFinish(void)
 {
 	SurfData_SetStage(m_strSurfData);
-	m_iMaterial = SurfData_Finish();
+
+	if (m_strSurfData)
+		m_iMaterial = SurfData_Finish();
+	else
+		m_iMaterial = -1;
 }
 void
 NSSurfacePropEntity::PropDataFinish(void)
 {
 	PropData_SetStage(m_strPropData);
-	m_iPropData = PropData_Finish();
+
+	if (m_strPropData)
+		m_iPropData = PropData_Finish();
+	else
+		m_iPropData = -1;
 }
 #else
 float
diff --git a/src/shared/surfaceproperties.qc b/src/shared/surfaceproperties.qc
index 734ddd03..bbd9e1cc 100644
--- a/src/shared/surfaceproperties.qc
+++ b/src/shared/surfaceproperties.qc
@@ -489,10 +489,10 @@ SurfData_Impact(entity e, int fl, vector org, vector ang)
 	} else { /* anything with takedamage = DAMAGE_YES is a NSurfacePropEntity. */
 		NSSurfacePropEntity foo = (NSSurfacePropEntity)e;
 
-		if (foo.GetSurfaceData(SURFDATA_MATERIAL) == -1)
-			SurfData_Impact_SurfaceParm(e, fl, org, ang);
-		else
+		if (foo.HasSurfaceData() && foo.GetSurfaceData(SURFDATA_MATERIAL) != -1)
 			FX_Impact(foo.GetSurfaceData(SURFDATA_FX_IMPACT), org, ang);
+		else
+			SurfData_Impact_SurfaceParm(e, fl, org, ang);
 	}
 }
 #endif