diff --git a/data/mods/TEST_DATA/items.json b/data/mods/TEST_DATA/items.json
index ac9320bf24aa3..993657d4db9ae 100644
--- a/data/mods/TEST_DATA/items.json
+++ b/data/mods/TEST_DATA/items.json
@@ -2391,16 +2391,16 @@
         "encumbrance": [ 12, 25 ],
         "material": [
           { "type": "cotton", "covered_by_mat": 100, "thickness": 1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 }
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 }
         ]
       },
       {
@@ -2409,16 +2409,16 @@
         "encumbrance": [ 12, 25 ],
         "material": [
           { "type": "cotton", "covered_by_mat": 100, "thickness": 1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 }
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 }
         ]
       },
       {
@@ -2427,16 +2427,51 @@
         "encumbrance": [ 12, 25 ],
         "material": [
           { "type": "cotton", "covered_by_mat": 100, "thickness": 1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 },
-          { "type": "steel", "covered_by_mat": 80, "thickness": 0.1 }
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 0.3 }
+        ]
+      }
+    ]
+  },
+  {
+    "id": "test_portion_segmented_armor",
+    "type": "ARMOR",
+    "name": "Segmented armor",
+    "copy-from": "test_swat_armor",
+    "armor": [
+      {
+        "covers": [ "torso", "head", "mouth", "eyes" ],
+        "coverage": 100,
+        "encumbrance": [ 12, 25 ],
+        "material": [
+          { "type": "cotton", "covered_by_mat": 100, "thickness": 1 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 3 }
+        ]
+      },
+      {
+        "covers": [ "leg_l", "leg_r", "foot_l", "foot_r" ],
+        "coverage": 100,
+        "encumbrance": [ 12, 25 ],
+        "material": [
+          { "type": "cotton", "covered_by_mat": 100, "thickness": 1 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 3 }
+        ]
+      },
+      {
+        "covers": [ "arm_l", "arm_r", "hand_l", "hand_r" ],
+        "coverage": 100,
+        "encumbrance": [ 12, 25 ],
+        "material": [
+          { "type": "cotton", "covered_by_mat": 100, "thickness": 1 },
+          { "type": "steel", "covered_by_mat": 80, "thickness": 3 }
         ]
       }
     ]
diff --git a/src/item_factory.cpp b/src/item_factory.cpp
index adaf8229fe2bb..e1e6e64fe9fbc 100644
--- a/src/item_factory.cpp
+++ b/src/item_factory.cpp
@@ -788,7 +788,13 @@ void Item_factory::finalize_post( itype &obj )
                 // scale the value of portion covered based on how much total is covered
                 // if you proportionally only cover 5% of the arm but overall cover 50%
                 // you actually proportionally cover 10% of the armor
-                mat.cover = static_cast<float>( mat.cover ) / ( static_cast<float>( it.coverage ) / 100.0f );
+
+                // in case of 0 coverage just say the mats cover it all
+                if( it.coverage == 0 ) {
+                    mat.cover = 100;
+                } else {
+                    mat.cover = static_cast<float>( mat.cover ) / ( static_cast<float>( it.coverage ) / 100.0f );
+                }
             }
         }
 
diff --git a/tests/coverage_test.cpp b/tests/coverage_test.cpp
index ef1995ed90d8f..4c4ef1611ecc8 100644
--- a/tests/coverage_test.cpp
+++ b/tests/coverage_test.cpp
@@ -28,7 +28,7 @@ static constexpr tripoint badguy_pos( HALF_MAPSIZE_X + 1, HALF_MAPSIZE_Y, 0 );
 static void check_near( std::string subject, float actual, const float expected,
                         const float tolerance )
 {
-    THEN( string_format( "%s is about %.1f (+/- %.1f) with val %.1f", subject, expected, tolerance,
+    THEN( string_format( "%s is about %.1f (+/- %.2f) with val %.1f", subject, expected, tolerance,
                          actual ) ) {
         CHECK( actual == Approx( expected ).margin( tolerance ) );
     }
@@ -175,10 +175,9 @@ TEST_CASE( "Proportional armor material resistances", "[material]" )
 
     SECTION( "Multi material segmented armor vs. melee" ) {
         const float dmg = get_avg_melee_dmg( "test_multi_portion_segmented_armor" );
+        const float base_line = get_avg_melee_dmg( "test_portion_segmented_armor" );
         // our armor should NOT be near 1 mm cloth + 80% of 1mm of steel
         // and should be higher (so lower damage) since they can overlap
-        // this is cut damage of 12 so shouldn't be near 6 with small variance
-        // if it is someone broke material rolls
-        check_not_near( "Average damage", dmg, 6.0f, 0.1f );
+        check_not_near( "Average damage", dmg, base_line, 0.05f );
     }
 }