diff --git a/R/class-workbook.R b/R/class-workbook.R
index 10ddd888a..c461de01d 100644
--- a/R/class-workbook.R
+++ b/R/class-workbook.R
@@ -658,7 +658,7 @@ wbWorkbook <- R6::R6Class(
                 # sheet name instead of the clone source
 
                 chart <- self$charts$chart[chartid]
-                self$charts$rels[chartid] <- gsub("?drawing[0-9].xml", paste0("drawing", chartid, ".xml"), self$charts$rels[chartid])
+                self$charts$rels[chartid] <- gsub("?drawing[0-9]+.xml", paste0("drawing", chartid, ".xml"), self$charts$rels[chartid])
 
                 guard_ws <- function(x) {
                   if (grepl(" ", x)) x <- shQuote(x, type = "sh")
@@ -5996,7 +5996,7 @@ wbWorkbook <- R6::R6Class(
       stylesInd        <- grep("styles\\.xml",                               self$workbook.xml.rels)
       themeInd         <- grep("theme/theme[0-9]+.xml",                      self$workbook.xml.rels)
       connectionsInd   <- grep("connections.xml",                            self$workbook.xml.rels)
-      customXMLInd     <- grep("customXml/item[0-9].xml",                    self$workbook.xml.rels)
+      customXMLInd     <- grep("customXml/item[0-9]+.xml",                   self$workbook.xml.rels)
       extRefInds       <- grep("externalLinks/externalLink[0-9]+.xml",       self$workbook.xml.rels)
       sharedStringsInd <- grep("sharedStrings.xml",                          self$workbook.xml.rels)
       tableInds        <- grep("table[0-9]+.xml",                            self$workbook.xml.rels)
@@ -6006,7 +6006,7 @@ wbWorkbook <- R6::R6Class(
 
       ## Reordering of workbook.xml.rels
       ## don't want to re-assign rIds for pivot tables or slicer caches
-      pivotNode        <- grep("pivotCache/pivotCacheDefinition[0-9].xml",  self$workbook.xml.rels, value = TRUE)
+      pivotNode        <- grep("pivotCache/pivotCacheDefinition[0-9]+.xml", self$workbook.xml.rels, value = TRUE)
       slicerNode       <- grep("slicerCache[0-9]+.xml",                     self$workbook.xml.rels, value = TRUE)
 
       ## Reorder children of workbook.xml.rels
diff --git a/R/wb_load.R b/R/wb_load.R
index 291aa1367..1a56e5c67 100644
--- a/R/wb_load.R
+++ b/R/wb_load.R
@@ -466,7 +466,7 @@ wb_load <- function(file, xlsxFile = NULL, sheet, data_only = FALSE) {
     cache_keep <- unlist(
       regmatches(
         wb$pivotTables.xml.rels,
-        gregexpr("(?<=pivotCache/pivotCacheDefinition)[0-9](?=\\.xml)",
+        gregexpr("(?<=pivotCache/pivotCacheDefinition)[0-9]+(?=\\.xml)",
                  wb$pivotTables.xml.rels,
                  perl = TRUE, ignore.case = TRUE
         )
@@ -1196,7 +1196,7 @@ wb_load <- function(file, xlsxFile = NULL, sheet, data_only = FALSE) {
       )
     }
 
-    for (cstitm in seq_along(grep_xml("customXml/item[0-9].xml"))) {
+    for (cstitm in seq_along(grep_xml("customXml/item[0-9]+.xml"))) {
 
       # TODO provide a function that creates a wb_rels data frame
       wb_rels <- rbindlist(xml_attr(wb$workbook.xml.rels, "Relationship"))