diff --git a/source/build/src/polymost.cpp b/source/build/src/polymost.cpp
index 94660737f..c83df3b82 100644
--- a/source/build/src/polymost.cpp
+++ b/source/build/src/polymost.cpp
@@ -38,6 +38,8 @@ typedef struct { float x, cy[2], fy[2]; int32_t tag; int16_t n, p, ctag, ftag; }
 #define VSPMAX 2048 //<- careful!
 static vsptyp vsp[VSPMAX];
 static int32_t gtag;
+static float xbl, xbr;
+int32_t domost_rejectcount;
 
 static float dxb1[MAXWALLSB], dxb2[MAXWALLSB];
 
@@ -3562,6 +3564,13 @@ static void polymost_domost(float x0, float y0, float x1, float y1)
         y1 += DOMOST_OFFSET; //necessary?
     }
 
+    // Test if span is outside screen bounds
+    if (x1+DOMOST_OFFSET < xbl || x0-DOMOST_OFFSET > xbr)
+    {
+        domost_rejectcount++;
+        return;
+    }
+
     vec2f_t const dm0 = { x0, y0 };
     vec2f_t const dm1 = { x1, y1 };
 
@@ -5296,6 +5305,7 @@ static void polymost_initmosts(const float * px, const float * py, int const n)
 
     int32_t vcnt = 1; //0 is dummy solid node
 
+    xbl = px[imin];
     vsp[vcnt].x = px[imin];
     vsp[vcnt].cy[0] = vsp[vcnt].fy[0] = py[imin];
     vcnt++;
@@ -5344,6 +5354,8 @@ static void polymost_initmosts(const float * px, const float * py, int const n)
         }
     } while (i != j);
 
+    xbr = px[i];
+
     if (px[i] > vsp[vcnt-1].x)
     {
         vsp[vcnt].x = px[i];
@@ -5351,6 +5363,8 @@ static void polymost_initmosts(const float * px, const float * py, int const n)
         vcnt++;
     }
 
+    domost_rejectcount = 0;
+
     vsp_finalize_init(vcnt);
     gtag = vcnt;
 }