diff --git a/log/tmfmt_logger.go b/log/tmfmt_logger.go
index 2b464a6b0..d03979718 100644
--- a/log/tmfmt_logger.go
+++ b/log/tmfmt_logger.go
@@ -35,7 +35,8 @@ type tmfmtLogger struct {
 }
 
 // NewTMFmtLogger returns a logger that encodes keyvals to the Writer in
-// Tendermint custom format.
+// Tendermint custom format. Note complex types (structs, maps, slices)
+// formatted as "%+v".
 //
 // Each log event produces no more than one call to w.Write.
 // The passed Writer must be safe for concurrent use by multiple goroutines if
@@ -103,7 +104,10 @@ KeyvalueLoop:
 			}
 		}
 
-		if err := enc.EncodeKeyval(keyvals[i], keyvals[i+1]); err != nil {
+		err := enc.EncodeKeyval(keyvals[i], keyvals[i+1])
+		if err == logfmt.ErrUnsupportedValueType {
+			enc.EncodeKeyval(keyvals[i], fmt.Sprintf("%+v", keyvals[i+1]))
+		} else if err != nil {
 			return err
 		}
 	}
diff --git a/log/tmfmt_logger_test.go b/log/tmfmt_logger_test.go
index 62eb32a03..a07b323c6 100644
--- a/log/tmfmt_logger_test.go
+++ b/log/tmfmt_logger_test.go
@@ -30,8 +30,10 @@ func TestTMFmtLogger(t *testing.T) {
 	assert.Regexp(t, regexp.MustCompile(`N\[.+\] unknown \s+ a=1 err=error\n$`), buf.String())
 
 	buf.Reset()
-	err := logger.Log("std_map", map[int]int{1: 2}, "my_map", mymap{0: 0})
-	assert.NotNil(t, err)
+	if err := logger.Log("std_map", map[int]int{1: 2}, "my_map", mymap{0: 0}); err != nil {
+		t.Fatal(err)
+	}
+	assert.Regexp(t, regexp.MustCompile(`N\[.+\] unknown \s+ std_map=map\[1:2\] my_map=special_behavior\n$`), buf.String())
 
 	buf.Reset()
 	if err := logger.Log("level", "error"); err != nil {