diff --git a/src/Intervals.php b/src/Intervals.php
index d889d0ad..a4800c5d 100644
--- a/src/Intervals.php
+++ b/src/Intervals.php
@@ -150,16 +150,37 @@ public static function compactConstraint(ConstraintInterface $constraint)
             $constraints[] = $intervals['numeric'][0]->getStart();
             $hasNumericMatchAll = true;
         } else {
+            // A bare != N matches all dev-* versions, so if the numeric part is the whole line minus some points,
+            // only compact it into unbounded != constraints when the branches already match all dev versions
+            $numeric = $intervals['numeric'];
+            $count = \count($numeric);
+            $skipNotEqual = false;
+            if (!$intervals['branches']['exclude'] && $count > 1
+                && (string) $numeric[0]->getStart() === (string) Interval::fromZero()
+                && (string) $numeric[$count - 1]->getEnd() === (string) Interval::untilPositiveInfinity()
+            ) {
+                $skipNotEqual = true;
+                for ($i = 0; $i < $count - 1; $i++) {
+                    if ($numeric[$i]->getEnd()->getOperator() !== '<'
+                        || $numeric[$i + 1]->getStart()->getOperator() !== '>'
+                        || $numeric[$i]->getEnd()->getVersion() !== $numeric[$i + 1]->getStart()->getVersion()
+                    ) {
+                        $skipNotEqual = false;
+                        break;
+                    }
+                }
+            }
+
             $unEqualConstraints = array();
-            for ($i = 0, $count = \count($intervals['numeric']); $i < $count; $i++) {
-                $interval = $intervals['numeric'][$i];
+            for ($i = 0; $i < $count; $i++) {
+                $interval = $numeric[$i];
 
                 // if current interval ends with < N and next interval begins with > N we can swap this out for != N
                 // but this needs to happen as a conjunctive expression together with the start of the current interval
                 // and end of next interval, so [>=M, <N] || [>N, <P] => [>=M, !=N, <P] but M/P can be skipped if
                 // they are zero/+inf
-                if ($interval->getEnd()->getOperator() === '<' && $i+1 < $count) {
-                    $nextInterval = $intervals['numeric'][$i+1];
+                if (!$skipNotEqual && $interval->getEnd()->getOperator() === '<' && $i+1 < $count) {
+                    $nextInterval = $numeric[$i+1];
                     if ($interval->getEnd()->getVersion() === $nextInterval->getStart()->getVersion() && $nextInterval->getStart()->getOperator() === '>') {
                         // only add a start if we didn't already do so, can be skipped if we're looking at second
                         // interval in [>=M, <N] || [>N, <P] || [>P, <Q] where unEqualConstraints currently contains
diff --git a/tests/IntervalsTest.php b/tests/IntervalsTest.php
index 457d8e39..bbc22771 100644
--- a/tests/IntervalsTest.php
+++ b/tests/IntervalsTest.php
@@ -51,6 +51,43 @@ public function testCompactConstraint($expected, $toCompact, $conjunctive)
         $this->assertSame((string) $expected, (string) $new);
     }
 
+    /**
+     * @dataProvider compactDevSafetyProvider
+     * @param array<string> $toCompact
+     * @param bool $conjunctive
+     */
+    public function testCompactConstraintKeepsMatchedSet($toCompact, $conjunctive)
+    {
+        $parser = new VersionParser;
+
+        $parts = array();
+        foreach ($toCompact as $part) {
+            $parts[] = $parser->parseConstraints($part);
+        }
+        $constraint = new MultiConstraint($parts, $conjunctive);
+
+        $compacted = Intervals::compactConstraint($constraint);
+        $dev = new Constraint('==', 'dev-foo');
+
+        $this->assertSame($constraint->matches($dev), $compacted->matches($dev), (string) $compacted);
+        $this->assertTrue(Intervals::isSubsetOf($compacted, $constraint), (string) $compacted);
+        $this->assertTrue(Intervals::isSubsetOf($constraint, $compacted), (string) $compacted);
+    }
+
+    public static function compactDevSafetyProvider()
+    {
+        return array(
+            'whole line minus one point, no dev' => array(array('> 1.0.0 != 2.0.0', '< 1.9.0'), false),
+            'whole line minus two points, no dev' => array(array('> 1.0.0 != 2.0.0 != 3.0.0', '< 1.5'), false),
+            'whole line minus one point, named branch' => array(array('> 1.0.0 != 2.0.0', '< 1.5', 'dev-bar'), false),
+            'whole line minus two points, named branch' => array(array('> 1.0.0 != 2.0.0 != 3.0.0', '< 1.5', 'dev-bar'), false),
+            'bounded != group' => array(array('> 1.0.0 != 2.0.0 < 3.0.0', '< 1.5', '>= 5.0'), false),
+            'conjunctive !=, all dev' => array(array('!= 2.0', '!= 3.0'), true),
+            'conjunctive != with excluded branch' => array(array('!= 2.0', '!= dev-foo'), true),
+            'disjunctive != with named branch' => array(array('!= 2.0', 'dev-bar'), false),
+        );
+    }
+
     public static function compactProvider()
     {
         return array(
@@ -114,6 +151,21 @@ public static function compactProvider()
                 array('!= 1.0', '!= 1.0', '!= dev-foo', '1.0.5.*'),
                 false
             ),
+            'whole line minus one point without dev does not become a bare !=' => array(
+                '< 2.0.0.0-stable || > 2.0.0',
+                array('> 1.0.0 != 2.0.0', '< 1.9.0'),
+                false
+            ),
+            'whole line minus two points without dev does not become a bare !=' => array(
+                '< 2.0.0.0-stable || > 2.0.0 < 3.0.0.0-stable || > 3.0.0',
+                array('> 1.0.0 != 2.0.0 != 3.0.0', '< 1.5'),
+                false
+            ),
+            'whole line minus two points with named branch does not become a bare !=' => array(
+                '< 2.0.0.0-stable || > 2.0.0 < 3.0.0.0-stable || > 3.0.0 || dev-bar',
+                array('> 1.0.0 != 2.0.0 != 3.0.0', '< 1.5', 'dev-bar'),
+                false
+            ),
             'conjunctive with complex negation' => array(
                 '1.0.5.*',
                 array('!= 1.0', '!= 1.0', '!= dev-foo', '1.0.5.*'),