diff --git a/code/renderergl1/tr_terrain.c b/code/renderergl1/tr_terrain.c
index bcbab3da..10f73a15 100644
--- a/code/renderergl1/tr_terrain.c
+++ b/code/renderergl1/tr_terrain.c
@@ -144,7 +144,7 @@ static void R_InterpolateVert(terraTri_t *pTri, terrainVert_t *pVert)
     pMinHeight  = (byte *)Q_min((uintptr_t)pVert0->pHgt, (uintptr_t)pVert1->pHgt);
     pMaxHeight  = (byte *)Q_max((uintptr_t)pVert0->pHgt, (uintptr_t)pVert1->pHgt);
     pVert->pHgt = (byte *)(pMinHeight + ((pMaxHeight - pMinHeight) >> 1));
-    assert(pVert->pHgt >= pMinHeight && pVert->pHgt < pMaxHeight);
+    assert(pVert->pHgt >= pMinHeight && pVert->pHgt < pMaxHeight || pMinHeight == pMaxHeight);
 
     // Calculate the average Z
     pVert->fHgtAvg = (float)(*pVert0->pHgt + *pVert1->pHgt);
diff --git a/code/renderergl2/tr_terrain.c b/code/renderergl2/tr_terrain.c
index 61fa1f2d..94c5fff2 100644
--- a/code/renderergl2/tr_terrain.c
+++ b/code/renderergl2/tr_terrain.c
@@ -141,7 +141,7 @@ static void R_InterpolateVert(terraTri_t *pTri, terrainVert_t *pVert)
     pMinHeight  = (byte *)Q_min((uintptr_t)pVert0->pHgt, (uintptr_t)pVert1->pHgt);
     pMaxHeight  = (byte *)Q_max((uintptr_t)pVert0->pHgt, (uintptr_t)pVert1->pHgt);
     pVert->pHgt = (byte *)(pMinHeight + ((pMaxHeight - pMinHeight) >> 1));
-    assert(pVert->pHgt >= pMinHeight && pVert->pHgt < pMaxHeight);
+    assert(pVert->pHgt >= pMinHeight && pVert->pHgt < pMaxHeight || pMinHeight == pMaxHeight);
 
     // Calculate the average Z
     pVert->fHgtAvg = (float)(*pVert0->pHgt + *pVert1->pHgt);