diff --git a/src/bees-context.cc b/src/bees-context.cc
index 0c5a69e..a1d3471 100644
--- a/src/bees-context.cc
+++ b/src/bees-context.cc
@@ -337,19 +337,29 @@ BeesContext::scan_one_extent(const BeesFileRange &bfr, const Extent &e)
 	if (e.flags() & Extent::PREALLOC) {
 		// Prealloc is all zero and we replace it with a hole.
 		// No special handling is required here.  Nuke it and move on.
-		BEESLOGINFO("prealloc extent " << e);
-		// Must not extend past EOF
-		auto extent_size = min(e.end(), bfr.file_size()) - e.begin();
-		BeesFileRange prealloc_bfr(m_ctx->tmpfile()->make_hole(extent_size));
-		BeesRangePair brp(prealloc_bfr, bfr);
-		// Raw dedup here - nothing else to do with this extent, nothing to merge with
-		if (m_ctx->dedup(brp)) {
-			BEESCOUNT(dedup_prealloc_hit);
-			BEESCOUNTADD(dedup_prealloc_bytes, e.size());
-			return bfr;
-		} else {
-			BEESCOUNT(dedup_prealloc_miss);
-		}
+		Task(
+			"dedup_prealloc",
+			[m_ctx, bfr, e]() {
+				BEESLOGINFO("prealloc extent " << e);
+				// Must not extend past EOF
+				auto extent_size = min(e.end(), bfr.file_size()) - e.begin();
+				// Must hold tmpfile until dedupe is done
+				auto tmpfile = m_ctx->tmpfile();
+				BeesFileRange prealloc_bfr(tmpfile->make_hole(extent_size));
+				// Apparently they can both extend past EOF
+				BeesFileRange copy_bfr(bfr.fd(), e.begin(), e.begin() + extent_size);
+				BeesRangePair brp(prealloc_bfr, copy_bfr);
+				// Raw dedup here - nothing else to do with this extent, nothing to merge with
+				if (m_ctx->dedup(brp)) {
+					BEESCOUNT(dedup_prealloc_hit);
+					BEESCOUNTADD(dedup_prealloc_bytes, e.size());
+					// return bfr;
+				} else {
+					BEESCOUNT(dedup_prealloc_miss);
+				}
+			}
+		).run();
+		return bfr; // if dedup success, which we now blindly assume
 	}
 
 	// OK we need to read extent now