diff --git a/source/gl_rsurf.c b/source/gl_rsurf.c
index aaaa984..14c625e 100644
--- a/source/gl_rsurf.c
+++ b/source/gl_rsurf.c
@@ -460,7 +460,7 @@ void R_DrawSequentialPoly (msurface_t *s)
 				theRect = &lightmap_rectchange[i];
 				glTexSubImage2D(GL_TEXTURE_2D, 0, 0, theRect->t, 
 					BLOCK_WIDTH, theRect->h, gl_lightmap_format, GL_UNSIGNED_BYTE,
-					lightmaps+(i* BLOCK_HEIGHT + theRect->t) *BLOCK_WIDTH*lightmap_bytes);
+					lightmaps[i] + (theRect->t * BLOCK_WIDTH) * lightmap_bytes);
 				theRect->l = BLOCK_WIDTH;
 				theRect->t = BLOCK_HEIGHT;
 				theRect->h = 0;
@@ -571,7 +571,7 @@ void R_BlendLightmaps (void)
 			theRect = &lightmap_rectchange[i];
 			glTexSubImage2D(GL_TEXTURE_2D, 0, 0, theRect->t, 
 				BLOCK_WIDTH, theRect->h, gl_lightmap_format, GL_UNSIGNED_BYTE,
-				lightmaps+(i* BLOCK_HEIGHT + theRect->t) *BLOCK_WIDTH*lightmap_bytes);
+				lightmaps[i] + (theRect->t * BLOCK_WIDTH) * lightmap_bytes);
 			theRect->l = BLOCK_WIDTH;
 			theRect->t = BLOCK_HEIGHT;
 			theRect->h = 0;
@@ -663,7 +663,7 @@ dynamic:
 				theRect->w = (fa->light_s-theRect->l)+smax;
 			if ((theRect->h + theRect->t) < (fa->light_t + tmax))
 				theRect->h = (fa->light_t-theRect->t)+tmax;
-			base = lightmaps[fa->lightmaptexturenum] + fa->light_t * BLOCK_WIDTH * lightmap_bytes + fa->light_s * lightmap_bytes;
+			base = lightmaps[fa->lightmaptexturenum] + (fa->light_t * BLOCK_WIDTH + fa->light_s) * lightmap_bytes;
 			R_BuildLightMap (fa, base, BLOCK_WIDTH*lightmap_bytes);
 		}
 	}
@@ -720,7 +720,7 @@ dynamic:
 				theRect->w = (fa->light_s-theRect->l)+smax;
 			if ((theRect->h + theRect->t) < (fa->light_t + tmax))
 				theRect->h = (fa->light_t-theRect->t)+tmax;
-			base = lightmaps[fa->lightmaptexturenum] + fa->light_t * BLOCK_WIDTH * lightmap_bytes + fa->light_s * lightmap_bytes;
+			base = lightmaps[fa->lightmaptexturenum] + (fa->light_t * BLOCK_WIDTH + fa->light_s) * lightmap_bytes;
 			R_BuildLightMap (fa, base, BLOCK_WIDTH*lightmap_bytes);
 		}
 	}