diff --git a/src/render/opengl/SDL_render_gl.c b/src/render/opengl/SDL_render_gl.c
index eb9d790..514ca27 100644
--- a/src/render/opengl/SDL_render_gl.c
+++ b/src/render/opengl/SDL_render_gl.c
@@ -914,9 +914,9 @@
         const GLfloat yend = verts[3];
 
         if (ystart == yend) {  /* horizontal line */
-            verts[2] += (xend > xstart) ? 1.0f : -1.0f;
+            verts[(xend > xstart) ? 2 : 0] += 1.0f;
         } else if (xstart == xend) {  /* vertical line */
-            verts[3] += (yend > ystart) ? 1.0f : -1.0f;
+            verts[(yend > ystart) ? 3 : 1] += 1.0f;
         } else {  /* bump a pixel in the direction we are moving in. */
             const GLfloat deltax = xend - xstart;
             const GLfloat deltay = yend - ystart;
diff --git a/src/render/opengles/SDL_render_gles.c b/src/render/opengles/SDL_render_gles.c
index e6350f0..49878c8 100644
--- a/src/render/opengles/SDL_render_gles.c
+++ b/src/render/opengles/SDL_render_gles.c
@@ -587,9 +587,9 @@
         const GLfloat yend = verts[3];
 
         if (ystart == yend) {  /* horizontal line */
-            verts[2] += (xend > xstart) ? 1.0f : -1.0f;
+            verts[(xend > xstart) ? 2 : 0] += 1.0f;
         } else if (xstart == xend) {  /* vertical line */
-            verts[3] += (yend > ystart) ? 1.0f : -1.0f;
+            verts[(yend > ystart) ? 3 : 1] += 1.0f;
         } else {  /* bump a pixel in the direction we are moving in. */
             const GLfloat deltax = xend - xstart;
             const GLfloat deltay = yend - ystart;
diff --git a/src/render/opengles2/SDL_render_gles2.c b/src/render/opengles2/SDL_render_gles2.c
index f0801ab..20743fe 100644
--- a/src/render/opengles2/SDL_render_gles2.c
+++ b/src/render/opengles2/SDL_render_gles2.c
@@ -811,9 +811,9 @@
         const GLfloat yend = verts[3];
 
         if (ystart == yend) {  /* horizontal line */
-            verts[2] += (xend > xstart) ? 1.0f : -1.0f;
+            verts[(xend > xstart) ? 2 : 0] += 1.0f;
         } else if (xstart == xend) {  /* vertical line */
-            verts[3] += (yend > ystart) ? 1.0f : -1.0f;
+            verts[(yend > ystart) ? 3 : 1] += 1.0f;
         } else {  /* bump a pixel in the direction we are moving in. */
             const GLfloat deltax = xend - xstart;
             const GLfloat deltay = yend - ystart;