diff --git a/pruning/keep_grid.go b/pruning/keep_grid.go
index a62c9c9..2dffc07 100644
--- a/pruning/keep_grid.go
+++ b/pruning/keep_grid.go
@@ -99,17 +99,21 @@ func (a retentionGridAdaptor) LessThan(b retentiongrid.Entry) bool {
 // Prune filters snapshots with the retention grid.
 func (p *KeepGrid) KeepRule(snaps []Snapshot) (destroyList []Snapshot) {
 
-	snaps = filterSnapList(snaps, func(snapshot Snapshot) bool {
+	matching, notMatching := partitionSnapList(snaps, func(snapshot Snapshot) bool {
 		return p.re.MatchString(snapshot.Name())
 	})
-	if len(snaps) == 0 {
-		return nil
+
+	// snaps that don't match the regex are not kept by this rule
+	destroyList = append(destroyList, notMatching...)
+
+	if len(matching) == 0 {
+		return destroyList
 	}
 
 	// Build adaptors for retention grid
 	adaptors := make([]retentiongrid.Entry, 0)
-	for i := range snaps {
-		adaptors = append(adaptors, retentionGridAdaptor{snaps[i]})
+	for i := range matching {
+		adaptors = append(adaptors, retentionGridAdaptor{matching[i]})
 	}
 
 	// determine 'now' edge
@@ -122,9 +126,8 @@ func (p *KeepGrid) KeepRule(snaps []Snapshot) (destroyList []Snapshot) {
 	_, removea := p.retentionGrid.FitEntries(now, adaptors)
 
 	// Revert adaptors
-	destroyList = make([]Snapshot, len(removea))
 	for i := range removea {
-		destroyList[i] = removea[i].(retentionGridAdaptor).Snapshot
+		destroyList = append(destroyList, removea[i].(retentionGridAdaptor).Snapshot)
 	}
 	return destroyList
 }
diff --git a/pruning/keep_helpers.go b/pruning/keep_helpers.go
index a756ce7..7c31d68 100644
--- a/pruning/keep_helpers.go
+++ b/pruning/keep_helpers.go
@@ -10,6 +10,17 @@ func filterSnapList(snaps []Snapshot, predicate func(Snapshot) bool) []Snapshot
 	return r
 }
 
+func partitionSnapList(snaps []Snapshot, predicate func(Snapshot) bool) (sTrue, sFalse []Snapshot) {
+	for i := range snaps {
+		if predicate(snaps[i]) {
+			sTrue = append(sTrue, snaps[i])
+		} else {
+			sFalse = append(sFalse, snaps[i])
+		}
+	}
+	return
+}
+
 func shallowCopySnapList(snaps []Snapshot) []Snapshot {
 	c := make([]Snapshot, len(snaps))
 	copy(c, snaps)
diff --git a/pruning/pruning_test.go b/pruning/pruning_test.go
index 0927333..9a33e7a 100644
--- a/pruning/pruning_test.go
+++ b/pruning/pruning_test.go
@@ -75,6 +75,10 @@ func TestPruneSnapshots(t *testing.T) {
 		},
 	}
 
+	reltime := func(secs int64) time.Time {
+		return time.Unix(secs, 0)
+	}
+
 	tcs := map[string]testCase{
 		"simple": {
 			inputs: inputs["s1"],
@@ -121,6 +125,24 @@ func TestPruneSnapshots(t *testing.T) {
 			},
 			expDestroy: map[string]bool{},
 		},
+		"multiple_grids_with_disjoint_regexes": {
+			inputs: []Snapshot{
+				stubSnap{"p1_a", false, reltime(4)},
+				stubSnap{"p2_a", false, reltime(5)},
+				stubSnap{"p1_b", false, reltime(14)},
+				stubSnap{"p2_b", false, reltime(15)},
+				stubSnap{"p1_c", false, reltime(29)},
+				stubSnap{"p2_c", false, reltime(30)},
+			},
+			rules: []KeepRule{
+				MustNewKeepGrid("^p1_", `1x10s | 1x10s`),
+				MustNewKeepGrid("^p2_", `1x10s | 1x10s`),
+			},
+			expDestroy: map[string]bool{
+				"p1_a": true,
+				"p2_a": true,
+			},
+		},
 	}
 
 	testTable(tcs, t)