diff --git a/src/terminal/Tabstops.zig b/src/terminal/Tabstops.zig
index 8955447f2..7e74bc961 100644
--- a/src/terminal/Tabstops.zig
+++ b/src/terminal/Tabstops.zig
@@ -14,7 +14,6 @@ const tripwire = @import("../tripwire.zig");
 const Allocator = std.mem.Allocator;
 const testing = std.testing;
 const assert = @import("../quirks.zig").inlineAssert;
-const fastmem = @import("../fastmem.zig");
 
 /// Unit is the type we use per tabstop unit (see file docs).
 const Unit = u8;
@@ -138,24 +137,21 @@ pub fn resize(
         return;
     }
 
-    // What we need in the dynamic size
-    const size = cols - prealloc_columns;
-    if (size <= self.dynamic_stops.len) {
+    // Number of units needed beyond the preallocated columns.
+    const dynamic_count = std.math.divCeil(
+        usize,
+        cols - prealloc_columns,
+        unit_bits,
+    ) catch unreachable;
+    if (dynamic_count <= self.dynamic_stops.len) {
         self.cols = cols;
         return;
     }
 
-    // Note: we can probably try to realloc here but I'm not sure it matters.
     try tw.check(.dynamic_alloc);
-    const new = try alloc.alloc(Unit, size);
-    errdefer comptime unreachable;
-    @memset(new, 0);
-    if (self.dynamic_stops.len > 0) {
-        fastmem.copy(Unit, new, self.dynamic_stops);
-        alloc.free(self.dynamic_stops);
-    }
-
-    self.dynamic_stops = new;
+    const old_len = self.dynamic_stops.len;
+    self.dynamic_stops = try alloc.realloc(self.dynamic_stops, dynamic_count);
+    @memset(self.dynamic_stops[old_len..], 0);
     self.cols = cols;
 }
 
@@ -208,21 +204,27 @@ test "Tabstops: dynamic allocations" {
     var t: Tabstops = .{};
     defer t.deinit(testing.allocator);
 
-    // Grow the capacity by 2.
+    // Grow by less than one unit to verify the allocation rounds up.
     const cap = t.capacity();
-    try t.resize(testing.allocator, cap * 2);
+    try t.resize(testing.allocator, cap + 5);
+    try testing.expectEqual(cap + unit_bits, t.capacity());
 
     // Set something that was out of range of the first
-    t.set(cap + 5);
-    try testing.expect(t.get(cap + 5));
-    try testing.expect(!t.get(cap + 4));
+    t.set(cap + 4);
+    try testing.expect(t.get(cap + 4));
+    try testing.expect(!t.get(cap + 3));
+
+    // Growing again preserves existing stops and clears the new unit.
+    try t.resize(testing.allocator, cap + unit_bits + 1);
+    try testing.expect(t.get(cap + 4));
+    try testing.expect(!t.get(cap + unit_bits));
 
     // Prealloc still works
     try testing.expect(!t.get(5));
 }
 
 test "Tabstops: resize to existing capacity does not allocate" {
-    var backing: [prealloc_columns]Unit = undefined;
+    var backing: [prealloc_count]Unit = undefined;
     var fixed = std.heap.FixedBufferAllocator.init(&backing);
     var t: Tabstops = .{};