diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index e99538e..adc999f 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -6,14 +6,14 @@ jobs:
   test:
     strategy:
       matrix:
-        go-versions: [ 1.14.x, 1.15.x, 1.16.x ]
+        version: [ '1.15', '1.16', '1.17' ]
         platform: [ ubuntu-latest, macos-latest, windows-latest ]
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Install Go
       uses: actions/setup-go@v2
       with:
-        go-version: ${{ matrix.go-version }}
+        go-version: ${{ matrix.version }}
     - name: Checkout code
       uses: actions/checkout@v2
     - name: Build
diff --git a/funcr/funcr.go b/funcr/funcr.go
index b23ab96..166e245 100644
--- a/funcr/funcr.go
+++ b/funcr/funcr.go
@@ -408,8 +408,9 @@ func (f Formatter) prettyWithFlags(value interface{}, flags uint32, depth int) s
 			if i > 0 {
 				buf.WriteByte(',')
 			}
+			k, _ := v[i].(string) // sanitize() above means no need to check success
 			// arbitrary keys might need escaping
-			buf.WriteString(prettyString(v[i].(string)))
+			buf.WriteString(prettyString(k))
 			buf.WriteByte(':')
 			buf.WriteString(f.prettyWithFlags(v[i+1], 0, depth+1))
 		}