diff --git a/index_test.go b/index_test.go
index 7fb3abf0c..df663c0cb 100644
--- a/index_test.go
+++ b/index_test.go
@@ -357,6 +357,7 @@ func TestBM25(t *testing.T) {
 	indexMapping := NewIndexMapping()
 	indexMapping.TypeField = "type"
 	indexMapping.DefaultAnalyzer = "en"
+	indexMapping.DefaultSimilarity = index.BM25Similarity
 	documentMapping := NewDocumentMapping()
 	indexMapping.AddDocumentMapping("hotel", documentMapping)
 	indexMapping.StoreDynamic = false
diff --git a/mapping/index.go b/mapping/index.go
index 6399bef20..70b333e86 100644
--- a/mapping/index.go
+++ b/mapping/index.go
@@ -488,7 +488,14 @@ func (im *IndexMappingImpl) FieldMappingForPath(path string) FieldMapping {
 		return *fm
 	}
 
-	return FieldMapping{}
+	// the edge case where there are no field mapping defined for a path, just
+	// return all the field specific defaults from the index mapping.
+	fm = &FieldMapping{
+		Analyzer:      im.DefaultAnalyzer,
+		Similarity:    im.DefaultSimilarity,
+		SynonymSource: im.DefaultSynonymSource,
+	}
+	return *fm
 }
 
 // wrapper to satisfy new interface
diff --git a/search/scorer/scorer_term.go b/search/scorer/scorer_term.go
index 7c4d6fab9..5521e83ac 100644
--- a/search/scorer/scorer_term.go
+++ b/search/scorer/scorer_term.go
@@ -165,7 +165,7 @@ func (s *TermQueryScorer) scoreExplanation(tf float64, termMatch *index.TermFiel
 		saturationExplanation := &search.Explanation{
 			Value: k1 / (tf + k1*fieldNormVal),
 			Message: fmt.Sprintf("saturation(term:%s), k1=%f/(tf=%f + k1*fieldNorm=%f))",
-				termMatch.Term, tf, k1, fieldNormVal),
+				termMatch.Term, k1, tf, fieldNormVal),
 			Children: []*search.Explanation{fieldNormalizeExplanation},
 		}