@@ -75,6 +75,15 @@ func (p *Pep440) Search(versions []string) error {
 		return fmt.Errorf("%s", err)
 	}
 
+	// A pre-release only qualifies once no stable version satisfies the constraint.
+	for _, v := range p.versions {
+		if specifiers.Check(v) && !v.IsPreRelease() {
+			p.FoundVersion.ParsedVersion = v.String()
+			p.FoundVersion.OriginalVersion = v.Original()
+			return nil
+		}
+	}
+
 	for _, v := range p.versions {
 		if specifiers.Check(v) {
 			p.FoundVersion.ParsedVersion = v.String()
 
@@ -130,6 +130,30 @@ var (
 			ExpectedParsedVersion:   "1.0b2",
 			ExpectedOriginalVersion: "1.0b2",
 		},
+		{
+			// Constraint skips the pre-release in favor of the highest matching stable version.
+			Pep440: Pep440{
+				Constraint: ">=15,<16",
+			},
+			Versions:                []string{"14.0.0", "15.6.1", "15.7.0b1", "16.0.0"},
+			SortedVersions:          []string{"16.0.0", "15.7.0b1", "15.6.1", "14.0.0"},
+			ExpectedInitErr:         nil,
+			ExpectedSearchErr:       nil,
+			ExpectedParsedVersion:   "15.6.1",
+			ExpectedOriginalVersion: "15.6.1",
+		},
+		{
+			// Constraint falls back to the highest matching pre-release when no stable version matches.
+			Pep440: Pep440{
+				Constraint: ">2.0",
+			},
+			Versions:                []string{"2.0", "2.1.0b3", "2.1.0rc2"},
+			SortedVersions:          []string{"2.1.0rc2", "2.1.0b3", "2.0"},
+			ExpectedInitErr:         nil,
+			ExpectedSearchErr:       nil,
+			ExpectedParsedVersion:   "2.1.0rc2",
+			ExpectedOriginalVersion: "2.1.0rc2",
+		},
 		{
 			// Empty constraint behaves identically to wildcard: skips pre-releases.
 			Pep440: Pep440{