diff --git a/zipper/protocols/prometheus/helpers/helpers.go b/zipper/protocols/prometheus/helpers/helpers.go
index b61f21f08..48c590642 100644
--- a/zipper/protocols/prometheus/helpers/helpers.go
+++ b/zipper/protocols/prometheus/helpers/helpers.go
@@ -139,29 +139,42 @@ func AdjustStep(start, stop, maxPointsPerQuery, minStep int64, forceMinStepInter
 // PromethizeTagValue - accept 'Tag=value' or 'Tag=~value' string and return sanitized version of it
 func PromethizeTagValue(tagValue string) (string, types.Tag) {
 	// Handle = and =~
-	t := types.Tag{}
-	idx := strings.Index(tagValue, "=")
-	if idx != -1 {
-		if tagValue[idx+1] == '~' {
+	var (
+		t       types.Tag
+		tagName string
+		idx     = strings.Index(tagValue, "=")
+	)
+
+	if idx < 0 {
+		return tagName, t
+	}
+
+	if idx > 0 && tagValue[idx-1] == '!' {
+		t.OP = "!"
+		tagName = tagValue[:idx-1]
+	} else {
+		tagName = tagValue[:idx]
+	}
+
+	switch {
+	case idx+1 == len(tagValue): // != or = with empty value
+		t.OP += "="
+	case tagValue[idx+1] == '~':
+		if len(t.OP) > 0 { // !=~
+			t.OP += "~"
+		} else { // =~
 			t.OP = "=~"
-			t.TagValue = tagValue[idx+2:]
-		} else {
-			t.OP = "="
-			t.TagValue = tagValue[idx+1:]
 		}
-	} else {
-		// Handle != and !=~
-		idx = strings.Index(tagValue, "!")
-		if tagValue[idx+2] == '~' {
-			t.OP = "!~"
-			t.TagValue = tagValue[idx+3:]
-		} else {
-			t.OP = "!="
+
+		if idx+2 < len(tagValue) { // check is not empty value
 			t.TagValue = tagValue[idx+2:]
 		}
+	default: // != or = with value
+		t.OP += "="
+		t.TagValue = tagValue[idx+1:]
 	}
 
-	return tagValue[:idx], t
+	return tagName, t
 }
 
 // SplitTagValues - For given tag-value list converts it to more usable map[string]Tag, where string is TagName
diff --git a/zipper/protocols/prometheus/helpers/helpers_test.go b/zipper/protocols/prometheus/helpers/helpers_test.go
index ee0ac3d64..f0df54ce8 100644
--- a/zipper/protocols/prometheus/helpers/helpers_test.go
+++ b/zipper/protocols/prometheus/helpers/helpers_test.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/go-graphite/carbonapi/tests/compare"
 	"github.com/go-graphite/carbonapi/zipper/protocols/prometheus/types"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestAlignValues(t *testing.T) {
@@ -161,3 +162,91 @@ func TestAdjustStep(t *testing.T) {
 		})
 	}
 }
+
+func TestPromethizeTagValue(t *testing.T) {
+	testCases := []struct {
+		name     string
+		tagValue string
+		wantName string
+		wantTag  types.Tag
+	}{
+		{
+			name: "empty string",
+		},
+		{
+			name:     "string without '='",
+			tagValue: "test>test",
+		},
+		{
+			name:     "check '='",
+			tagValue: "name=1",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "=", TagValue: "1"},
+		},
+		{
+			name:     "check '!='",
+			tagValue: "name!=1",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "!=", TagValue: "1"},
+		},
+		{
+			name:     "check '=~'",
+			tagValue: "name=~1",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "=~", TagValue: "1"},
+		},
+		{
+			name:     "check '!=~'",
+			tagValue: "name!=~1",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "!~", TagValue: "1"},
+		},
+		{
+			name:     "check '!=~' with empty name",
+			tagValue: "!=~1",
+			wantName: "",
+			wantTag:  types.Tag{OP: "!~", TagValue: "1"},
+		},
+		{
+			name:     "check '=~' with empty name",
+			tagValue: "=~1",
+			wantName: "",
+			wantTag:  types.Tag{OP: "=~", TagValue: "1"},
+		},
+		{
+			name:     "check '=' with empty value",
+			tagValue: "name=",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "="},
+		},
+		{
+			name:     "check '!=' with empty value",
+			tagValue: "name!=",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "!="},
+		},
+		{
+			name:     "check '!=~' with empty value",
+			tagValue: "name!=~",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "!~"},
+		},
+		{
+			name:     "check '=~' with empty value",
+			tagValue: "name=~",
+			wantName: "name",
+			wantTag:  types.Tag{OP: "=~"},
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			gotName, gotTag := PromethizeTagValue(tt.tagValue)
+
+			assert.Equal(t, tt.wantName, gotName)
+			assert.Equal(t, tt.wantTag, gotTag)
+		})
+
+	}
+
+}