diff --git a/src/pci.rs b/src/pci.rs
index 8e02bde4..4495bf99 100644
--- a/src/pci.rs
+++ b/src/pci.rs
@@ -295,14 +295,16 @@ impl PciDevice {
                     panic!("I/O BARs are not supported on this platform");
                 }
             } else {
-                // bits 2-1 are the type 0 is 32-but, 2 is 64 bit
+                // bits 2-1 are the type 0 is 32-bit, 2 is 64 bit
                 match bar >> 1 & 3 {
                     0 => {
                         self.bars[current_bar].bar_type = PciBarType::MemorySpace32;
                         self.bars[current_bar].address = u64::from(bar & 0xffff_fff0);
 
                         self.write_u32(current_bar_offset, 0xffff_ffff);
-                        let size = !(self.read_u32(current_bar_offset) & 0xffff_fff0) + 1;
+                        let size = (!(self.read_u32(current_bar_offset) & 0xffff_fff0))
+                            .checked_add(1)
+                            .unwrap_or(0);
                         self.bars[current_bar].size = u64::from(size);
                         self.write_u32(current_bar_offset, bar);
                     }