diff --git a/src/lib/notcurses.c b/src/lib/notcurses.c
index 2ed84e0d3..53fa3c90c 100644
--- a/src/lib/notcurses.c
+++ b/src/lib/notcurses.c
@@ -2005,14 +2005,21 @@ int ncplane_polyfill_yx(ncplane* n, int y, int x, const cell* c){
 static int
 calc_gradient_component(unsigned tl, unsigned tr, unsigned bl, unsigned br,
                         int y, int x, int ylen, int xlen){
-  assert(xlen >= 2);
-  assert(ylen >= 2);
   assert(y >= 0);
   assert(y < ylen);
   assert(x >= 0);
   assert(x < xlen);
   const int avm = (ylen - 1) - y;
   const int ahm = (xlen - 1) - x;
+  if(xlen < 2){
+    if(ylen < 2){
+      return tl;
+    }
+    return (tl * avm + bl * y) / (ylen - 1);
+  }
+  if(ylen < 2){
+    return (tl * ahm + tr * x) / (xlen - 1);
+  }
   const int tlc = ahm * avm * tl;
   const int blc = ahm * y * bl;
   const int trc = x * avm * tr;
@@ -2066,6 +2073,9 @@ int ncplane_gradient(ncplane* n, const char* egc, uint32_t attrword,
      channel_palindex_p(lr) || channel_palindex_p(ur)){
     return -1;
   }
+  if(egc == NULL){
+    return -1;
+  }
   int yoff, xoff, ymax, xmax;
   ncplane_cursor_yx(n, &yoff, &xoff);
   // must be at least 1x1, with its upper-left corner at the current cursor
@@ -2084,14 +2094,18 @@ int ncplane_gradient(ncplane* n, const char* egc, uint32_t attrword,
   const int ylen = ystop - yoff + 1;
   if(ylen == 1){
     if(xlen == 1){
-      // single cell FIXME
+      if(ul != ur || ur != lr || lr != ll){
+        return -1;
+      }
     }else{
-      // horizontal 1d FIXME
+      if(ul != ll || ur != lr){
+        return -1;
+      }
     }
-    return 0;
   }else if(xlen == 1){
-    // vertical 1d FIXME
-    return 0;
+    if(ul != ur || ll != lr){
+      return -1;
+    }
   }
   for(int y = yoff ; y <= ystop ; ++y){
     for(int x = xoff ; x <= xstop ; ++x){
diff --git a/tests/fills.cpp b/tests/fills.cpp
index b30b66b58..eb572b65e 100644
--- a/tests/fills.cpp
+++ b/tests/fills.cpp
@@ -219,7 +219,7 @@ TEST_CASE("Fills") {
       }
     }
     CHECK(0 == notcurses_render(nc_));
-    // attr should change, but not the EGC/color
+    // EGC/color should change, but nothing else
     CHECK(0 == ncplane_cursor_move_yx(n_, 0, 0));
     uint64_t channels = 0;
     channels_set_fg_rgb(&channels, 0x88, 0x99, 0x77);
@@ -237,6 +237,52 @@ TEST_CASE("Fills") {
     }
   }
 
+  // test the single-cell (1x1) special case
+  SUBCASE("GradientSingleCell") {
+    int sbytes;
+    CHECK(0 == ncplane_set_fg(n_, 0x444444));
+    CHECK(1 == ncplane_putegc_yx(n_, 0, 0, "A", &sbytes));
+    CHECK(0 == notcurses_render(nc_));
+    CHECK(0 == ncplane_cursor_move_yx(n_, 0, 0));
+    uint64_t channels = 0;
+    channels_set_fg_rgb(&channels, 0x88, 0x99, 0x77);
+    channels_set_bg(&channels, 0);
+    REQUIRE(0 == ncplane_gradient(n_, "A", 0, channels, channels, channels, channels, 0, 0));
+    CHECK(0 == notcurses_render(nc_));
+    cell d = CELL_TRIVIAL_INITIALIZER;
+    CHECK(1 == ncplane_at_yx(n_, 0, 0, &d));
+    CHECK(channels == d.channels);
+    REQUIRE(cell_simple_p(&d));
+    CHECK('A' == d.gcluster);
+  }
+
+  // 1d gradients over multiple cells
+  SUBCASE("Gradient1D") {
+    int sbytes;
+    CHECK(0 == ncplane_set_fg(n_, 0x444444));
+    CHECK(1 == ncplane_putegc_yx(n_, 0, 0, "A", &sbytes));
+    CHECK(0 == notcurses_render(nc_));
+    CHECK(0 == ncplane_cursor_move_yx(n_, 0, 0));
+    uint64_t chan1 = 0, chan2 = 0;
+    channels_set_fg_rgb(&chan1, 0x88, 0x99, 0x77);
+    channels_set_fg_rgb(&chan2, 0x77, 0x99, 0x88);
+    channels_set_bg(&chan1, 0);
+    channels_set_bg(&chan2, 0);
+    REQUIRE(0 == ncplane_gradient(n_, "A", 0, chan1, chan2, chan1, chan2, 0, 3));
+    CHECK(0 == notcurses_render(nc_));
+    cell d = CELL_TRIVIAL_INITIALIZER;
+    CHECK(1 == ncplane_at_yx(n_, 0, 0, &d));
+    CHECK(chan1 == d.channels);
+    REQUIRE(cell_simple_p(&d));
+    CHECK('A' == d.gcluster);
+    CHECK(0 == ncplane_cursor_move_yx(n_, 0, 0));
+    REQUIRE(0 == ncplane_gradient(n_, "A", 0, chan2, chan1, chan2, chan1, 0, 3));
+    CHECK(1 == ncplane_at_yx(n_, 0, 0, &d));
+    REQUIRE(cell_simple_p(&d));
+    CHECK('A' == d.gcluster);
+    CHECK(chan2 == d.channels);
+  }
+
   CHECK(0 == notcurses_stop(nc_));
   CHECK(0 == fclose(outfp_));