diff --git a/docs/ACKNOWLEDGEMENTS.md b/docs/ACKNOWLEDGEMENTS.md
index a0596ab..cb942c9 100644
--- a/docs/ACKNOWLEDGEMENTS.md
+++ b/docs/ACKNOWLEDGEMENTS.md
@@ -92,5 +92,6 @@ is acknowledged and greatly appreciated:
  * [Thomas Bertels](https://codeberg.org/tbertels) - updated French translations ([#83](https://codeberg.org/a-j-wood/pv/pulls/83))
  * [kevinruddy](https://codeberg.org/kevinruddy) - added decimal units option ([#85](https://codeberg.org/a-j-wood/pv/pulls/85))
  * [xmort](https://codeberg.org/xmort) - added "`--output`" option ([#90](https://codeberg.org/a-j-wood/pv/pulls/90))
+ * [bogiord](https://codeberg.org/bogiord) - reported the loss of output block device size detection in 1.8.10 ([#91](https://codeberg.org/a-j-wood/pv/issues/91))
 
 ---
diff --git a/docs/NEWS.md b/docs/NEWS.md
index d491c88..d1654d9 100644
--- a/docs/NEWS.md
+++ b/docs/NEWS.md
@@ -1,3 +1,7 @@
+### UNRELEASED
+
+ * fix: correct the detection of output block device size that was broken in 1.8.10 ([#91](https://codeberg.org/a-j-wood/pv/issues/91))
+
 ### 1.8.10 - 15 June 2024
 
  * feature: new "`--output`" option to write to a file instead of standard output (pull request [#90](https://codeberg.org/a-j-wood/pv/pulls/90)) supplied by [xmort](https://codeberg.org/xmort)
diff --git a/src/main/main.c b/src/main/main.c
index 12d5d89..fdabb9e 100644
--- a/src/main/main.c
+++ b/src/main/main.c
@@ -194,27 +194,6 @@ int main(int argc, char **argv)
 		pv_state_inputfiles(state, opts->argc, (const char **) (opts->argv));
 	}
 
-	/* Total size calculation, in normal transfer mode. */
-	if (0 == opts->watch_pid) {
-		/*
-		 * If no size was given, try to calculate the total size.
-		 */
-		if (0 == opts->size) {
-			pv_state_linemode_set(state, opts->linemode);
-			pv_state_null_terminated_lines_set(state, opts->null_terminated_lines);
-			opts->size = pv_calc_total_size(state);
-			debug("%s: %llu", "no size given - calculated", opts->size);
-		}
-
-		/*
-		 * If the size is unknown, we cannot have an ETA.
-		 */
-		if (opts->size < 1) {
-			opts->eta = false;
-			debug("%s", "size unknown - ETA disabled");
-		}
-	}
-
 	/*
 	 * If stderr is not a terminal and we're neither forcing output nor
 	 * outputting numerically, we will have nothing to display at all.
@@ -264,9 +243,57 @@ int main(int argc, char **argv)
 	if (opts->interval > 600)
 		opts->interval = 600;
 
+	/*
+	 * Set output file, treating no output or "-" as stdout; we have to
+	 * do this before looking at setting the size, as the size
+	 * calculation looks at the output file if the input size can't be
+	 * calculated (issue #91).
+	 */
+	if (NULL == opts->output || 0 == strcmp(opts->output, "-")) {
+		pv_state_output_set(state, STDOUT_FILENO, "(stdout)");
+	} else {
+		int fd = open(opts->output, O_WRONLY | O_CREAT | O_TRUNC, 0600);	/* flawfinder: ignore */
+		/*
+		 * flawfinder rationale: the output filename has been
+		 * explicitly provided, and in many cases the operator will
+		 * want to write to device files and other special
+		 * destinations, so there is no sense-checking we can do to
+		 * make this safer.
+		 */
+		if (fd < 0) {
+			fprintf(stderr, "%s: %s: %s\n", opts->program_name, opts->output, strerror(errno));
+			pv_state_free(state);
+			opts_free(opts);
+			return PV_ERROREXIT_ACCESS;
+		}
+		pv_state_output_set(state, fd, opts->output);
+	}
+
+	/* Total size calculation, in normal transfer mode. */
+	if (0 == opts->watch_pid) {
+		/*
+		 * If no size was given, try to calculate the total size.
+		 */
+		if (0 == opts->size) {
+			pv_state_linemode_set(state, opts->linemode);
+			pv_state_null_terminated_lines_set(state, opts->null_terminated_lines);
+			opts->size = pv_calc_total_size(state);
+			debug("%s: %llu", "no size given - calculated", opts->size);
+		}
+
+		/*
+		 * If the size is unknown, we cannot have an ETA.
+		 */
+		if (opts->size < 1) {
+			opts->eta = false;
+			debug("%s", "size unknown - ETA disabled");
+		}
+	}
+
 	/*
 	 * Copy parameters from options into main state.
 	 */
+
 	pv_state_interval_set(state, opts->interval);
 	pv_state_width_set(state, opts->width, opts->width_set_manually);
 	pv_state_height_set(state, opts->height, opts->height_set_manually);
@@ -300,29 +327,6 @@ int main(int argc, char **argv)
 			    opts->fineta, opts->rate, opts->average_rate,
 			    opts->bytes, opts->bufpercent, opts->lastwritten, opts->name);
 
-	/*
-	 * Set output file, treating no output or "-" as stdout
-	 */
-	if (NULL == opts->output || 0 == strcmp(opts->output, "-")) {
-		pv_state_output_set(state, STDOUT_FILENO, "(stdout)");
-	} else {
-		int fd = open(opts->output, O_WRONLY | O_CREAT | O_TRUNC, 0600);	/* flawfinder: ignore */
-		/*
-		 * flawfinder rationale: the output filename has been
-		 * explicitly provided, and in many cases the operator will
-		 * want to write to device files and other special
-		 * destinations, so there is no sense-checking we can do to
-		 * make this safer.
-		 */
-		if (fd < 0) {
-			fprintf(stderr, "%s: %s: %s\n", opts->program_name, opts->output, strerror(errno));
-			pv_state_free(state);
-			opts_free(opts);
-			return PV_ERROREXIT_ACCESS;
-		}
-		pv_state_output_set(state, fd, opts->output);
-	}
-
 #ifdef MAKE_OUTPUT_NONBLOCKING
 	/*
 	 * Try and make the output use non-blocking I/O.